My kids have had tablets since they were young. No delays anywhere (except in the one that has adhd/autism, but that was always there and I just didn't notice til he was 6 and couldn't manage things his older siblings could manage at the same age, but at that stage I was used to hangin out with quirky homeschooled kids so he was just quirky).

I never restricted screens so they use them for everything from entertainment to research. No pacifying. Okay except maybe on long car trips but that's as much to alleviate their boredom as to make sure I don't crash the car getting distracted by them fighting XP

I've been told by adults that my kids are very sociable and intelligent and that talking to them is like talking to mini adults. My daughter has only started being rude (aka firmly glued to her phone and doing the rolling eyes exasperated sigh thing when told to get off and be polite/sociable at least for a little while) since she decided to try out high school (she's just completed her first term after having never been), but it could also be all that fun transitioning to a teenager stuff that may have happened even if she'd stayed homeschooling.

Their creativity hasn't been stifled in any way, my boys can still come up with intricate roleplaying games on the fly when they decide to play together, or build things including solving logistical problems, and my daughter can still produce amazing cards when she's doing birthday cards or invitations for her own parties.

I don't think you're overreacting (much) though. My older two learned to self-regulate most things pretty early and it's just my adhd child that I need to monitor and occasionally assist with strategies to wind down and transition off (he's better now). I've known other parents that have had similar issues as I've had with my adhd child, and you may need to help out there til they're mature enough to figure it out (or til they move out and it's not your problem anymore XD).