Yes and no. I do blame the lack of quality on the screenwriter and director of Nemesis because they were ... at the helm (cough). I won't blame Abrams simply because he's the new guy but I am incredibly skeptical of his creative output. He leaves a lot of things in other people's lap (he left Alias midway to develop Lost and took a lot of the creative force from the former to the later. Alias suffered and has never regained the same level of quality since)
The problem with Nemesis was the screenwriter. The movie's many problems are lodged in its core, not somewhere later on in development - and I certainly wouldn't run the people in charge of the franchise at the time (Rick Berman and Brannon Braga).
As for the director... I don't really think it matters who directs a Star Trek movie. Lets face it: going on to the film you know exactly who will be cast in it (and they've had the character worked out for decades), you know exactly what it's going to look like (no room for unique visual stylings or odd camera angles)... this is why Paramount has been fine with giving the *director* slot to former actors with no previous experience -- Nimoy, Shatner, Frakes... directing a giant movie sounds like a dangerous thing to you and I, but compared to the average movie a Star Trek film is a bike on autopilot with thirty sets of training wheels.
For Nemesis, the director was certainly an idiot... but in all honesty, so was Nick Meyer - and his movies were great. Their commentaries on the DVDs are divorced from reality in exactly the same way -- Meyer rants about how angry he is that the viewscreen wasn't made of glass while Baird rages about how important Tom Hardy is. Neither of them seems to be clear on exactly what a Star Trek movie is or what makes it good.
I'm curious as to what you refer to as a "mistake" exactly. You and I have discussed that the ST movies are nothing like the show - but I also thought as blase as Insurrection was, it was also the closest to the original ST forumla (for TNG, anyway).
It's a simple theory: the TOS movies are completely divorced from their series, the TNG movies are not. The TOS movies had great crossover success... the TNG movies did not. The TNG movies did well with First Contact, which was the least like the show...
All the TNG movies were, basically, continuations of the TV show. The TOS movies are *nothing* like the series and require no grand understanding of continuity or admittance to the sci fi fandom brotherhood... they're darned entertaining films that can stand on their own right. Going to see a TNG movie felt like you were watching TNG Season 8.
They took very few risks with them -- look at the uniforms... when they did change them for the movies, the outfits immediately got shipped off to the ongoing DS9 series. No risk at all, no jump away from TV - you're just paying to watch the TV show you can catch in syndication. Compare that to the original movies, with those crimson uniforms that seemed to have no place anywhere... that was bold. That's all a single example that may seem small, but I think it holds up throughout: the TOS movies changed the characters on a fundamentally appealing level... the TNG movies, when they did anything, just unceremoniously dropped elements from the show which might confuse new viewers.
Now that's an overstatement.
We argue our points here, young man.