All those little changes aren't the reason, though they do show that the creators weren't able to come up with anything original (or thought fans would freak out about a pre-TOS series using lasers and non-photon torpedoes).
For me the reason the series didn't appeal to me was that it just didn't hit its mark. It should have been a series about brave men and women venturing out into the unknown and becoming the glue that would hold together numerous different races who would form the Federation.
Instead we get a bumbling fool tripping into every fist he comes across, getting more angry and aggressive, a pouty Vulcan (from a race that is far removed from the people we know them to be), a stereotypical Brit, and a token black guy who could've been on fire and you'd never have noticed.
The serialised nature of S3 showed how it worked and S4 gave us some proper Trek storytelling, but by then it was just too little too late. Before they made ENT they should've taken a break for a year or two, recharge their batteries, watch TOS again for inspiration (since it should've been ENT's closest comparison) and turn off the technobabble generator.