Do keep in mind that everyone is naturally one-sided. Imagine you’re going down a flight of stairs and are jumping to the bottom from the third or fourth stair up: almost every person will have a preferred “leg” to land on. Much like the right arm/side of the torso is more developed than the left on most people (what hand to you pick things up and carry with?) the same is said for the leg. People have a natural preference for stepping out with one leg over the other (if you are standing square, one foot is typically what you will start your stride with unless other impediments exist).
Of course other physiological issues can come into play (scoliosis is actually a fairly common culprit IME), but one leg being notably stronger/more capable than another isn’t uncommon and as riders we spend a looot of time compensating for it (and trying to even ourselves out).
There are a couple of thoughts on this… as someone who is extremely one sided (I am very weak on the left, both by nature - my dominant leg is the right - but also due to old injury). One: In your daily life, practice making your weak leg your dominant one. Instead of relying/falling back on the right leg, use the left. Mindfulness!
The second is actually what I have found most beneficial, though - riding is not necessarily an exercise in strength but rather, timing, finesse, and communication. Being strong is a part of it but for me, “My left leg is weak, I can’t MAKE him listen to my leg!” is a flaw of my logic. If I am asking for an exercise and the horse is ignoring my left leg (the exercise is hard and the horse does not wish to do it, and ignoring the left leg because it is weaker, is easier than doing the exercise) then my solution technically shouldn’t be “have a stronger left leg!” It should be “Have a horse that is more attentive to my aids and doesn’t try to ignore them.” If the timing of my left leg is good, and the aid from my left side is correct, then I need to hold my horse to the standard that they need to obey the cues. Working on reactivity and responsiveness to the aids (developing a more sensitive, attuned horse) means that the horse is no longer trying to cheat through my (less strong) left side.
And of course because nothing in riding is simple, the less strong I need to be on my left side for aids to go through, the more capable and strong my left side becomes because rather than riding bilaterally (thinking of myself in terms of halves, “He’s not listening to my left leg!” and engaging in a struggle over it) I am riding correctly, with good timing and good aids, which reduces my one-sidedness (sometimes using the right to compensate for the weaker left) so my weak side actually gets stronger.
Clear as mud, eh? 