YABU.
Not necessarily in your motives and parenting choices, but in your disparagement of everyone else's choices. We all do what we think best for our own DC at the time.
You may or may not be holding your DC back, I don't know them and even if I did, I wouldn't comment. However, those of us who do differently are not thrusting our DC forwards and trying to force them to grow up too quickly.
WRT to the e.g.s you gave, my 5yo watched her first film the month before her 5th birthday. She simply wasn't ready/didn't want to before then. It was Frozen, and she was desperate to watch it because she wanted to fit in with everyone else, having been playing Frozen games and singing frozen songs in the school playground without really knowing what it was about. She's watched one film since then which we all watched as a family, inc DS (2.6). We had a really lovely afternoon, but the DC aren't particularly interested in watching any more films just yet and would much rather read books. This doesn't make them 'better' children or us 'better' parents, it just shows that atm they don't have the attention span or the ability to process rapidly moving images and sound to enjoy films. Film is also a cultural art form, just as much as books are, so no need to be sneery.
Potty training - different methods for different DC. Both mine would have got really upset at being left to wander around without nappies/pants on. They also both hated being wet, even as babies. Both mine decided that they were 'big' now and asked for pants. We took them to the shops, let them choose their own pants, and that was it. DS is 2.6, he's never yet had an accident, though it'll happen sometime.
Babygros. YABVVVVVVVVU on this one! But I guess your DC didn't/don't have severe reflux? They are the most impractical things in the world. When the baby vomits, you have vom over a whole outfit, not just part of it. You need a toothpick to scrape it out of the poppers. You have to put your hands in the vom in order to undo it and then everything goes through the opening onto the baby (requiring a bath) and also slides off sideways onto whatever they're lying on. So much better to find tops with shoulder poppers, arms out, over the back of the head, then lift off top with vom inside. Whip new top on. Job done, no faffing about with dozens of poppers 20 times a day. You can even change them sitting up.
Also, whoever else said about Jersey-lined jeans is spot on. At 7m both mine were crawling well and cruising. Their little knees would have been shredded in babygros! There's also the inescapable fact that the crawling motion inevitable ends up with both legs stuck in the same babygro leg, leading to great distress.
Finally, dressing up. Call it 'growing up too fast' if you want to, but most people call it 'learning through imitation and role play'. Are you going to stop your toddler pretending to cook or make you a cup of tea as well? Because most people would think that opening ovens, pouring boiling water etc are not suitable activities for young DC and if you're not going to allow them to pretend to be grown-ups then you really ought to be consistent about it. Make sure you never allow your DC to climb into a toy car and pretend to drive it!