Honestly, I think it's a bit of a stretch for you to blame your parents for being an 'adult without any skills or hobbies' because they let you give up piano lessons when you wanted to.
For a start, you can pick up a hobby or skill at any age, and you certainly don't have to be good at it to enjoy it or participate in it.
For another, a child wanting to socialise with her friends at school break sounds like a perfectly reasonable reason to want to stop.
I didn't have any childhood skills/hobbies because we were dirt poor and it never occurred to my parents that music lessons or sports were a thing you did, even if the money had been there, but I've picked up choral singing, drystone walling, several languages, pottery, climbing, tai chi, print-making and other things in adulthood.
I also think that it's equally valid for a child to be allowed to drop an activity they don't enjoy, to listen to their own instincts, and to realise that once begun, something doesn't have to be continued without enjoyment. Especially if you've arrived at this decision because of your own past.
I feel like recently I've realised the small decisions we make as parents can be huge in the long run and I really want to get it right. I don't want resentment in the future but gratitude that we did everything possible to give them the best start in life!
I agree about the small decisions, but there's no such thing as a blanket 'getting it right'. Your children are still very young and 'the best start in life' does not mean enforced activities to make them 'skilful and interesting adults'.