To return to the title question, I don't think that Star Trek has been ruined at all. Every iteration has been completely different, appealing to audiences that have changed over time. In general, people these days are more aware of science, especially fictional science so the methods used in the older shows don't work as well.
As a little kid I loved watching reruns of TNG but they just don't hold up very well from a technical point of view. The scientific principles underpinning the TNG universe are changed all the time so that the writers could move the story along. It's not something that I noticed as a kid but it really stood out when I started re-watching it a couple of years ago. Voyager suffers from the same problem.
DS9 stands alone as a more procedural/personality driven show that I think stands the test of time a bit better just because it's not as focused on the science part of science fiction.
I was quite enjoying Enterprise before it was cancelled, if only for the different spin it put on the Star Trek universe (no all-powerful Federation to back them up, just flying by the seats of their pants). The decision to use the Vulcan as the sex symbol was questionable. You'd think that an advanced alien race would be able to create more realistic fake boobs...
The JJ Abrams movies were OK. Good action but probably would have benefited from including a bit more Trek lore instead of trying to appeal to a wider audience.
As for Disco, they didn't do themselves any favors by placing it immediately prior to the Kirk era. It forced them to go sideways to avoid screwing up the Trek universe timeline too much. As a result the story-lines are a little, different, shall we say than other Trek shows. Not bad, just different.
Sorry for the essay, I'm bored at work today.