Ah, the great “Doodle Debate”!
I can weigh in here with my experiences, and have noticed the Doodle trend growing exponentially during the 18-19 years I’ve been a trainer; 15 or 20 years ago they were more of a relative rarity.
The popularity of these designer breeds is indeed mostly a result of two things: “Trendiness”, and impatience.
Here is a list of the “designer mixes” I’ve had in my classes just in the past 9 months:
Goldendoodles, Labradoodles - too many to count (I have probably worked with at least 200 over the years.)
Bernadoodle (Berner/Poodle)
Sheepadoodle (Sheepdog/Poodle)
BenARDoodle - this one was a cross between a miniature! Poodle and a St. Bernard. Don’t ask me how, I would think A/I?, but not sure - where there’s a will there’s a way, so. (This one was a handful as a puppy - though surprisingly cute, go figure - a VERY excitable and largish hairy puppy with way more energy than most St. Bernard pups, and the owner was chronically frustrated by its behavior because she couldn’t do the necessary work. Being a F/T critical care nurse with two children under the age of 5? Puppy training just wasn’t going to happen - and she probably should have re-thought the whole timing of the puppy thing since the husband wasn’t on board, but oh well.)
Puggle (Obviously Pug/Beagle)
Aussidoodle (because we need dogs with MORE energy to drain off when we live in Suburbia!)
Cavishon (CKC Spaniel/Bichon)
Malti-poo - LOTS of those.
Schoodle (Schnauzer/Poodle - smart and stubborn!)
Maltipoo/Yorkipoo cross (Oy.)
Cavipoo (CKC/Poodle)
Shichon (Bichon/Shih Tzu)
There have been a lot more, but I don’t keep records more than a year old.
IME, most of the Doodles have a LOT of energy and tend to be excitable, but there are also some with bigtime anxiety issues; though it’s hard to know how much to blame this on the owners - the majority of whom are first timers so don’t exercise or socialize their dogs nearly enough. It seems to be the dog breed favored by a lot of people in the NoVa/D.C. area, many of who are new to the country, a lot of whom are Indian - many professional people who may not actually have the time for a dog, but feel that they need to have one (a lot of that going around), especially if they have kids. Since they have deeper pockets, money is not an issue and they will pay whatever it costs.
MANY, MANY people buy/acquire dogs on impulse, and do no research; the main reason for getting a Doodle? You guessed it - they are hypoallergenic (or so they are told.) The grooming is a problem, and since they will NOT groom the dog at home (too much work), the poor groomers stay busy. And then the people complain when their dog winds up “shaved.”
Doodle temperaments are a bit all over the map but I’ve had a number of good ones; they are generally intelligent (and respond well to clear, boundary setting, reward-based training), but they need WAY more exercise and engagement than they generally get - this is the “owner’s bad”, but it’s hard to explain to first timers that they need to schedule exercise, training, play, enrichment, outlets for their dogs - and that dogs don’t just “fall into line” during the first year because you “talk to them and explain WHY they are bad, and yell NO!! repeatedly.” SIGH
There are more “Poodly” Doodles who tend to take after the Poodle parent (I suspect these are the F1s), and I mention this to their owners when I work with them; they are more dignified and reserved, and don’t suffer fools gladly - but LOVE to work with you when you give them jobs to do and are leaderly, confident, and calm. They tend to affix themselves to me and not listen to their owners, so I have to repeatedly demonstrate how to take the role of leader, use well-timed reward, be clear and firm and fair and POSITIVE. Owners of Doodles think they shouldn’t have to “do the work” because Hey - it’s not a GSD, (or similar), so it should be “easy”, right??
The more excitable types (more like the Golden/Lab parent) will jump and jump and jump until the cows come home, and since the owners give the jumping intermittent reinforcement (because AWWWW! CUTE! FLUFFY!), it continues and intensifies - especially with the younger and teenaged dogs. (Often people have NO BOUNDARIES for their dogs, and then complain that they constantly “push boundaries” with endless attention seeking behavior - and the vast majority of them get insufficient exercise; I’ve had people tell me that they “just don’t exercise their Doodle”, and wonder why it has zero impulse control and thick, spongy fat over the ribs. 
)
I had one student awhile ago with a Doodle who went through Advanced with me (got her CGC and was working on Rally stuff), and she didn’t have him neutered because “He would be a great stud dog and should reproduce since he has such a good temperament!” (HeadDesk.) I guess she would breed him with what…Other F1s? Goldens? Poodles?
The strain of anxiety (and instability of temperament) in a percentage of Doodle is not all as a result of lack of socialization - just as often it’s a result of both irresponsible breeding and lack of health and temperament testing (as a number of people have mentioned above); these are not “great examples of their respective breeds”, but instead are a result of just breeding random Labs and Goldens to random Poodles; often turning out to be the worst of both worlds. Some of the anxious Doodles have that Poodle “sharpness” when their fear response is triggered, requiring the owner to step up to the plate and work on counter conditioning, focus, and desensitization. They often don’t, so the dog becomes a prisoner of its own “bad” behavior because it winds up leash and dog reactive so is confined to the house, not getting to “go places and do things” with its owner. Because everyone is so busy, owners don’t want to take the time to deal with it (same with the dogs who lack impulse control for different reasons.) Many Doodle buyers are NOT discerning, and they simply don’t know what they don’t know. (Again - they do NO research, but buy a dog only based on emotion.)
Health issues are also more common than they should be - especially in dogs under a year old.
One reason that there are so many of these dogs is greater availability; there are more irresponsible breeders who breed these designer litters (for profit), so it’s easier to find an available Doodle than it is to find a well-bred Poodle or Lab or Golden - at least for most people. The trendy aspect is also at play; people want what is “popular”, and are willing to pay 3-5 grand for it.
People are also impatient and do things on impulse - like their dogs do (LOL.) Languishing on a waiting list for a purebred (well bred) dog can be frustrating, and they aren’t willing to delay gratification - not to mention the barrier to entry for many first time dog owners; most legit breeders screen prospective homes and are more likely to sell to those who know the breed (or have networked successfully.)
There is the “cute” factor in play as well; people LOVE furry, fuzzy-faced puppies (I’ve had Husky owners tell me that the reason they chose the breed is because “the puppies look like an adorable stuffed animal!” ARGH!! I must question the Husky breeders who sell to these people, especially if they are fist time owners.) OTOH, I have seen Husky pups advertised on sales sites - we have one of those “Puppy stores” nearby, it sprang up in the place of one that was closed down a couple of years ago: Dreamy Puppy - which sold almost exclusively designer Toy breeds, often with LOTS of health issues), and the Husky pups on the site go for 5-6 grand. Obviously from the puppy mill pipeline. (One of my young students with a teenaged Husky gave it NO exercise, and when I asked: “do you know what your dog was bred to do?” was astonished when I told her. Facepalm.)
Anyway, I think this trend is here to stay for the aforementioned reasons. “Greeders” want to make money, people have money, and they want a dog. NOW.
Let me conclude by saying that I shouldn’t throw all Doodle owners under the bus. I’ve had a number of responsible people in my classes who have committed to training and improving their dogs!, have put the work in, and have wonderful dogs they can enjoy as a result; my hat is off to them. Those who don’t do justice to their high-energy, high needs dog? They probably shouldn’t own dogs in the first place - but unfortunately there is no way to police that. It’s America, after all.
