Part of it will have to do with your tolerance for what the 60s or the 80s or the 90s or even the 00s thought the future would be. Because if you don’t have tolerance for any of that, it’s best to start with one of the new shows like Discovery or Strange New Worlds.
If that isn’t an issue, I’d suggest going to this website and seeing which show’s summary appeals to you most and then dive in. It’s true that Star Trek shows (generally) start weak in their first season, but there are first season episodes we could also all recommend.
I grew up with TOS, so I will always go with TOS before the others, but I also recognize it can be pretty hard to get into a 1960s idea of the far future.