The problem with ENT was that although it was meant to be the precursor to TOS, it was written and produced as if it were the precursor to TNG and TOS never existed. Case in point: In the very first TOS episode, "The Cage," there are no phasers, they use lasers. And warp speed is a BIG deal, with the crew putting on goggles and hanging on for dear life. (They also refer to it as "time warp," which is interesting.) But on ENT, they already had "phase pistols" and warp speed was as routine as it is in every other Star Trek franchise.
The ENT Enterprise was supposed to be more primitive than good ole NCC-1701 from TOS, but it looked more sophisticated. So too was humanity's knowledge of the universe, meeting enemies like the Ferengi literally centuries before they should be known. By the end they were even using transporters pretty regularly, another slap in the face to established continuity.
ENT had a lot of potential. It could have been a fun, campy paean to not only TOS but classic science fiction in general, and explored some of those classic tropes through a modern lens. Instead it was just TNG III, VGR being TNG II. Say what you will about DS9, at least it wasn't the same exact thing again.
(Which is not to say that either of these series don't have some good episodes. ENT did some cool stuff with the Vulcans, showing the evolution of their society, as well as the with Andorians, a race from TOS that we hadn't seen very often. Similarly, VGR's "Year of Hell" cycle was terrific.)
