What are you doing on my lawn? And why does my back hurt?Part of it is the "imprint" factor, the first is always the best. If your starting on TOS, then yeah its absolutely the best. But if your a later trekkie that cut your teeth on TNG lets say, that can skew your opinion.
Edit: In all seriousness, you make a good point. When I first started watching Star Trek, it was only 13 years after it had been cancelled and I was just a little kid. So the acting style and production values weren't all that out of date for me. But if the first time you saw the original Star Trek was in 2019, well, that's a different ball of worms.