Yeah, my advice re: trimming had more to do with the absolute minimum you’ll need to do prior to adding a glue-on. If you glue something on to the existing trim without pretty substantial alterations, you’ll be absolutely no better off. The trim is honestly everything. You cannot shoe your way out of poor trimming and IME a lot of DIY gluing failures come from folks trying to glue a shoe over their farrier’s trim when the farrier’s trim, well, blows. The composite shoes are fantastic but they are still only as good as the trim and application.
You have more leeway if you’re doing barefoot with boots. You still likely won’t see as much progress in hoof morphology without additional trim management, which will continue to make boot fitting frustrating, but it will minimize how much hands on trimming you need to do and theoretically reduce the risk of pissing off your farrier.
At the end of the day, you have to decide if you will either do everything possible to get the feet better, or you will accept as good as you are going to get with the professionals you have at your disposal. I don’t think either option is wrong or makes you a bad horse owner. But it is a decision you have to make. If the horse is largely retired and comfortable enough…meh…have the current farrier put the shoes back on. If he’s not a satisfactory level of comfortable or you have hopes of maybe hacking him around…the rubber will hit the road at some point and you can kick that can further down the road and revisit it when it inevitably comes up again, or you can start the process of learning now, accept that there will be mistakes and blunders and frustration, and be that much closer to having a process that works for you and hopefully your horses.
I know it sucks to be in your shoes because I’ve been there. I feel for you.