The remastered blurays.
I have seen most of season one which is pretty good.
I think since the other series came along as technology improved and filmmaking as a whole grew some of the things like for example fight scenes are super corny and certain alien costumes.
If I watched it back in the 60s I bet I wouldn't feel this way and would absolutely love it.
I'm still determined to become a huge TOS lover and watch every episode eventually.
Trust me, as someone who watched it (well at least the third season) first run; and the rest as soon as it hit syndication a few months after the end of the network run; even for its time, some of the fight sequences were bad in terms of stunt doubles and continuity (IE the principal actor having a ripped shirt in close ups, yet when they get back to the longer shot with the stunt doubles, the rip/Tear is CLEARLY not there.

)
Also, while I agree Star Trek is a product of its time on TV (IE the 1960ies); I DISAGREE that the pacing/structure was so different/unique from the other shows of the period (especially other genre shows like 'Time Tunnel', 'Lost In Space', 'Voyage to the Bottom of the Sea', 'The Invaders', etc.
^^^
All the above had similar pacing, recurring crewmen/characters (even 'The Invaders' starting with its second season .)
IMO - GR's claim that 'Star Trek' was 'so new/different' or 'ahead of it's time' was just pandering to the already on board fanbase. Make no mistake it was a good show, and a good science fiction show, and still to date my absolute favorite series in what is now 'The Star Trek Franchise' -- but overall it was no better or worse than the other great genre shows of the period like the original (1960ies) 'Outer Limits' or 'The Twilight Zone'.
Believe me even back in the day, you had discussions of 'yeh, I like some of the moves inn the fight sequence between 'not-Kirk' and 'not-Khan'.
One thing I will say is that the first season was really filmed with a more feature film quality (again for the 1960ies) with regard to the sets in that (IMO) they were MUCH better lit to make them look more real then the plywood and cardboard they were.
Also, the Blu-Rays really do bring out UNWANTED detail that the director of photography NEVER expected would be visible to audiences. They were indeed on a budget (every show is, even today); and you have to remember when they were shooting the show, they KNEW where the end result would end up - on a 13" - 17" diagonal consumer TV using an aerial antenna and WAY lower resolution then even TVs made 20 years later. (if you still own an old style VHS VCR - put in an off cable or off the air recorded episode of TOS <--- That is probably the closest approximation of 1960ies era over the air TV resolution as even professionally transferred VHS tapes will look better.)
Many younger TOS fans laugh at the idea that in 'The Doomsday Machine' the producers made its registry 1017 (and not say '1710'), because they were concerned audiences might confuse it as being the actual Enterprise; but if you watched TV in the 1960ies over the air, you'd know that was in fact a valid concern at the time.
As to the 'why' someone may not like it; in the end, I think it comes down to personal tastes. I was born in 1963; but I still as a kid/teenager/young adult, found there were 'older' films (science fiction and otherwise) whose execution and effects looked VERY dated compared to what was 'modern' at the time (like Star Trek or Space 1999); but it still didn't detract from my enjoyment of them and really liking them at the time or to this day.