[q] they trivialized the romulans in Nemesis.[/q]
(some of this may contain spoilers for those of you that haven't watched Nemesis)
Indeed, they destroyed a very good and well developed plot device by completely thought half of the comments alone in Nemesis. (1) The Romulan senate and Tal Shiar is slightly less gullible than they appear to be (altho the Tal Shiar don't appear per se, surely they would have known what was going on? And ways to deal with it?).
(2) The female Romulan claims that the destruction of earth would be a stain on thier honour and the blood would be on the hands of thier children for generations. Since when did the romulan culture breed anything except a desire to destroy any enemy of the Star Empire? To elimenate the hated Federation?
If she had issues about going to war when peace was so close - that would've worked since the very first episode they appeared in has a Romulan commander lamenting "must it always be so" when a young officer points out that the sign for war is Romulan strengh in comparison to an enemy. However she would have been acting out of an argument that it was in the best interests of the Empire not to do it - but a crisis of concience? I think not.
Moreso, the Romulan warships that appear are pretty pathetic considering they knew exactly what the Scimitar was armed with. The Enterprise battle also lacked imagination, and there was no real feeling behind the actions of most of the actors.
Data's "goodbye" was impressive as a throwback to TNG days but it lacked substance since you never actually believed the Enterprise could be blow to hell if he didn't stop the reaction.
They've turned Picard into a Kirk character - the latter plots revolve around him constantly whereas in TNG, Generations (First Contact because it really established "canon" history of the warp launch) and even Insurrection, you could follow a plot that dealt with several key characters and thier lives. (Altho, Crusher kinda vanished after the end of TNG in terms of plot importance).
Before anyone complains to me I'm forgetting the format of older Trek, I'm not - think of the Khan-Genesis-Voyage Home (er..) arc? You followed Kirk, the crew and even the enemies through good plots without being focused on one man. Kirk, McCoy, Spock all have equal plot value. Hell, even Scotty got to make a play for screen importance during the clear choice he made about excelsior ("up yer shaft!").
[q]Brennan & Brag[/q]
B&B did some good work, but they should've walked away before Ent started. From what little I've seen (BBC lost the right to Trek now, so its on Channel 4 who've gone on a season break the length of a Q's lifetime) Ent suffers from the opposite fate to what TNG did - this time there's not enough been done to establish the characters, and the stories are being crammed in beside a very poor attempt to giving said characters more depth. No one really cares if Archer gets killed by the Suliban et al because he could be replaced by a far more charismatic and mature captain yet still be the rebellious NX-01 captain he has to be.
[q]Cuz post DomWar is a time where there are MANY storylines to be explored.[/q]
Very true, but that better not include Captain Riker and his mission to go around sucking everyone's cock to keep the Federation in one piece because we both know it'd end up being too weak for his style of character. Beyond which Jonathan Frakes really can't pull off the young confident yet sometimes still learning Riker anymore.
What would be nice would be a film showing what happened to the Enterprise crew during the Dominion war - they were.... 14th fleet? Dunno, but it'd be good to see, perhaps as a TV Movie that jumped a year per hour or so. It'd work because real trek fans could follow the characters as if Nemesis never happend (lets be honest, in our hearts it never reallly did...

) and it could explain a lot of the character's slight changes by Insurrection.

You could also tie it in with an upcoming DS9 movie, with guest appearances of that cast and references toward the end as to what will happen in that regard.