I don't think Brosnan's being "hard on himself" at all. He's not saying he failed to deliver what was expected of him, or that there were films (or even scenes) where he miserably botched the performance.
What he's saying (it seems to me) is that his tenure was uneven at best and pretty directionless, overall. "I felt I was caught in a time warp between Roger and Sean," he says, which I interpret as meaning the series was stuck in "hover" mode, trying to prolong the formula past its sell-by date and coasting along on momentum. Certainly it's hard not to get that impression from DAD, which is assembled Frankenstein-like from bits and pieces of earlier, better films.
"The violence was never real," he says, "the brute force of the man was never palpable." Here I detect his usual complaint that he wasn't allowed to "go tough" in the way Craig later was. But he's right that the violence was strictly cartoon fare, and thus at odds with the pretentious stabs at "serious characterization." Which brings us to...
"...the characterization didn't have a follow-through of reality, it was surface." This is probably the pithiest critique to me: all the Brosnan entries take a stab at making the character "deeper" or "more human" or "more real" through some artifice or other -- the disloyal friend, the back-stabbing love interest, the loved-then-lost-then-loved-again-then-killed girlfriend, the abandonment by M -- but ultimately they're all tacked-on, half-hearted and fake-feeling, just padding between copious sequences of cartoonish action and bad jokes. It's like trying to turn Moonraker into The English Patient by throwing in a couple of scenes from "Days of Our Lives." The best (worst?) example is "Die Another Day," where Bond is captured, tortured and left for dead by MI-6, only to show up bearded and soaking wet in his pajamas in the lobby of his hotel, in a scene played strictly for laughs. Rarely does a film change tone so completely and so quickly, and never does it go well.
I like that Brosnan is taking some responsibility for the wrong turns his films took, but I wouldn't interpret his remarks as "they gave me a job to do and I blew it." Indeed, the fact that he got to do it four times and brought in big bucks each time proves he was giving his bosses what they wanted, in spades. But I do think it's possible to look back on something you did earlier in your life or career -- even if it was considered a success at the time -- and wish it had gone differently. So I'm conflicted: on the one hand, I'm not sure what he could've done, personally, to change the direction of his entries, but on the other hand as the "point man" for those entries, the guy whose face is front and center, it's hard to resist the urge to pin a lot of it on him. Especially when, as I've noted, casting him was the first tip-off to where EON was planning to take us.