is probably attributable to certain biases or factors that dunked it a bit deeper into the tank.
For example maybe they liked the Directors more than the Director last time.
Maybe the Winter Soldier theme that has devastatingly bad source / title roots (in terms of potentially very bad buzz) is actually USA-bashing loon heaven for some of them. Critics are into metaphors and nudge-nudge wink-wink inside knowledge of what it all traces back to, and for some of them it may have given them enough of a *snicker* to up the rating. Critics have pre-existing biases, political or religious or otherwise. There was a Passion of the Christ reviewer who was one of the few giving it an F. I looked at his other reviews at the time and sure enough his very rare worsts were for a few Christian and specifically Catholic-themed movies.
A SPOILER here though I've deleted the key name to ease it. A few of the reviews I saw seemed to in a way bemoan that it didn't go far enough with the Winter Soldier theme, or suggest it was afraid to. Lumenick's review had this: "And to further remove it from any possible contemporary relevance, [villain name deleted] is working for the same group of “rogue’’ Nazis that the Cap tangled with in the 1940s (a distinction presumably aimed at not antagonizing the real-life descendants of mainstream Nazis)."
That's a funny line and of course part of the broader criticism many have about villains generally. There seem to be politically correct obstacles, as well as avoiding negative buzz obstacles, to what studios are willing to allow when it comes to villains. But one can still get the source and sensibilities, while understanding why things have to be toned down for a wannabe mega-blockbuster the studio wants to appeal to as broad a base as possible. If it at least has the nudge-nudge wink-wink snicker-worthiness and Source Material-Approved element for any given critic, it may well be enough for an uptick in their rating. They see and understand the metaphor, and they like it despite any frustration that it can't be as open or obvious as a few of them might wish.
Abandoning the magnificent romance of the first movie, in favor of the either romance-crippled dynamic, or bromance factor / metaphor if that's what's coming with Bucky Barnes for the next half a dozen movies, may also be a plus for some critics compared to the last movie. For me, it's probably the movie's biggest, most unforgivable sin in terms of the enormous lost opportunity to have continued to do something special.
Another factor may well be fear as Lumenick was mocking. Newspapers are in peril and so are related critic jobs. Advertisers have to be appeased and subscription cancellations avoided. Even Lumenick felt the need to temper his criticism to appease the angry hordes in advance, at least somewhat. The sequel to a successful first movie is likely to have more initial, not less, passionate support before people have even seen it.
So there are all kinds of factors that could easily account for the 79% vs. (so far at least) 92%. And they may well all be not just subjective, but conspicuously and laughably subjective when weighing scores like a 6.9/10 versus a 7.6/10. Ultimately it's just a small and biased as the next guy or gal group, on average more esoteric or whatever other adjectives apply, with a bigger soap box than the very small percentage of the population that even goes to see these movies including blockbusters.