I've been learning guitar for a couple of years (being already an experienced pianist), and it was very surprising to me how many different techniques need to be mastered to play guitar. I never got to the level on piano where the precise way I hit the keys mattered (apart from soft or loud). On a guitar how precisely you hold and move your fingers makes a massive difference. Hammer-on, pull-off, bends, slides, barring and holding down multiple strings with one finger, are all different techniques. Then there's exactly where you hold the finger in relation to the fret which can really change the sound (or in my case, be completely wrong). On your right hand, there's how you pick or strum, even whether you use a plectrum, the pads of your fingers, or your nails.

Then there’s muting with the palm or fret hand to assist with arpeggios etc.

I usually tell friends with kids looking to get them into music; start your kids on piano. Stringed instruments like guitar or violin unfortunately introduce an additional aspect of difficulty that turns off a lot of young students who just want to start making music.

i'm going through a similar learning experience: i've been playing the drums for nearly 3 decades and only now am i starting to learn jazz/swing and appreciate the extremely subtle dynamic variations that go into playing those rhythms (especially at lower volume). even something that seems as basic as switching to traditional grip can be a huge learning experience with a whole new set of small muscle groups to cultivate.

i think my guitar technique will always be pretty punk rock though :)