Marisa not being in top 5 makes sense. For all her damage she has bad anti airs, doesn't get nearly the same type of conversions off lights that other characters do, her specials are PP fodder, she's hella weak to lows, lots of recovery on her stuff.
Blanka on the flip side has one of the best anti air buttons in the game, has a flash kick Blanka ball for anti air and a reversal, jump back ball makes both approaching him annoying and can blow up someone trying to throw loop, that cr mp is a war crime, and his level 2 is some bullllllllllllllshit. Legitimately more bullshit than JP and Rashids level 2s, but make no mistake all 3 are some bullshit.
What keeps Blanka out is more like weaker matchups he does have/this game has a real strong group of top tiers (Luke, Chun, Cammy, Ken, Jp, guile. Deejay, Juri, Rashid). Outside of Luke n JP, who are locked top 5, could probably do the rest in any real order.