I haven't heard anyone say transformers is only for children in a long time. But I can tell you what's intended for children an my opinion.

Animated- In the beginning it was for kids, but I was a kid at this time and it was awesome, eventually it stopped being just for kids and went a bit mature. Anyone who is calling cyberverse the best animated transformers show obviously hasn't watched this.

Cyberverse- good-ish but obviously for children and extremely over hyped by people that either are children or WFC netflix was so bad it made Cyberverse look like the second coming of beast wars. It's honestly hard to watch because of line delivery and the overwhelming feeling of "This is literally for 6 year olds".

Rescue bots- Good but Obviously for children, all of them are pretty watch-able no matter the age group though.

RID 2015- WTF cartoon network, Prime wasn't for kids, why have you made this cringey sequel series that lacks tone and depth only until the final season; and only then it's half the time. Why is it even called RID when they're never hiding until the FINAL SEASON. Also wtf did you do to Grimlock, Sideswipe, and every other character, all you did was confirm that the timeline isn't connected to the games and even make the question of if this is an actual sequel to prime or an alternate continuity in the cluster like FOC.

Netflix BotBots- 100% for its target age group. In that capacity it looks perfectly fine, why is everybody crying over a tv show for literal pre-schoolers.

Tl:dr- some transformers things are for kids but the franchise is very much not, also Cyberverse is over rated and RID2015 is terrible.