It depends. Prequels that try to explain how this or this happened rarely, if not never, don't suck.
Films/shows with their own unrelated story that just so happen to be set before this other film/show can be just as good as any sequel, depending on who's working on it.
For example, Hannibal Rising is a prequel to the first book, and it focuses on young Hannibal Lecter and shows us his origin, how he came to be. It was a massive critical failure. The show, Hannibal, was about the relationship between Hannibal Lecter and Will Graham and just so happened to be set before Red Dragon. It was a massive critical success.
If this show is set before TNG, and tries telling us how this and this happened in TNG, rather than forming its own story and plot, it could suck.
I think that's sort of my point....while it is possible for a prequel not to be naff, there's a greater chance it will be.
(hannibal was quite popular over here, usually shown after elementary. It's not my cup of tea though.)
When you transplant it over to the Trek universe though, it automatically removes some of the options for story telling.....if it's definitely in the prime universe, none of the major planets can be threatened. Now, while 'saving the planet/universe' doesn't crop up so much in Trek, it automatically precludes any of that....there can be no 'best of both worlds' there can be no Dominion War style arc, there can be no existential threat to the federation...because we know the federation is fine, it's planets are in place.
Now admittedly, we always know things will be OK because our heroes always win, but that slight possibility of 'maybe not this time' goes out the window.
Can it work? Yeah, I think it could work. Lost Era set prequel is something I can see working, looking at forging the peace with the Klingon Empire, or even just doing its own thing. It just wouldn't get it's Big Moments like those I mention, at least not with all the potential tension.
So yeah, you are right, but for every successful prequel (and viewed objectively, the most famous of 'bad' prequels, the Star Wars ones, aren't even that bad) There's more that didn't work out so well. (caprica...enterprise...)
Perhaps it's because the audience that doesn't mind a predestined end just isn't big enough compared to those lost that get turned off by that sort of storytelling.
So, yeah....I would still prefer post Nemesis, wouldn't mind Lost Era, but anything before that wouldn't appeal and another reboot would have to really persuade me it was amazing to bother watching at all, (though if it's family friendly my toddler guarantees it will be watched religiously.)
Fingers crossed eh.