It has aged very well. It's difficult for me to be objective, because I enjoy old shows and don't care if they look corny by latest standards, it's all about ideas for me. However, my girlfriend has never seen Star Trek until 2017, I introduced her to The Cage (TOS) and it was too dated for her (she's 27) even though she liked the premise. But after I showed her several TNG episodes, she actually got really into it, to be point of asking if we can watch some Star Trek - great win for me. She asked how old the show was and it surprised her, she thought it was more recent. But I'm being very selective in what episodes I show.
If you like Star Trek for the Sci Fi ideas, then I don't think that it really matters how it looks, that's just a bonus. I love TOS and watch it all the time, even though I was born over two decades after it was cancelled.
The worst one to age, imho, is Voyager, just because how relatively recent it is, yet it looks like it was made in the 80s. What's with the bulky laptops? It's supposed to be the 24th century. I can see the makers of TOS not consulting the few futurists that existed back then, but Voyager's computers looked older than the ones that were actually in use at the same time in the 20th century.
For those who watch ST for action scenes... I think those suck in all the reincarnations, to be honest. OK, the explosions are pretty cool in the reboot movies, but it's hardly the reason to enjoy STAR TREK.