When the game was current, there were nearly zero known infinites for MSF. Of course, it’s easy to go back after 7+ years and say “dude this game has hella infinites,” but compared to XSF (which had a laundry list of known infinites before MSF even came out) it’s not even in the same league.
When MSF was current, the only remotely practical infinite was Spidey’s [s.strong-jab DP (1 hit)] * n. Wolvie’s 100% combo (speedup, c.fierce until dizzy, speedup, c.fierce * n, super) is not an infinite.
From a graphical standpoint, MSF is by far the worst of the Marvel games. Just check out something like Wolvie’s crouching animation from MSH to MSF. Putrid. The character portraits looks like they were done with crayons, the backgrounds are unimaginative palette swaps of XSF, the general color schemes are gaudy and tasteless. The sole redeeming graphical nicety was the transition animation when you tagged (Bison teleported out as partner tagged through him, BH disappeared into his hell portal, etc.); notably, these transitions were removed from MVC forward. The announcer was entertaining, for what that’s worth.
COTA, MSH and MVC1 are the only Marvel games that look like they had any sort of project director; I’ve always maintained that MSH is the best-looking CPS2 game ever made, with a clear sense of art and sound direction. XSF, MSF, and MVC2 look like they were just thrown together without much care (XSF to a slightly lesser extent, but not by much).
To answer the OP: MSF is disliked because it’s just boring. Outside of the furry rat problem, the game simply isn’t fun. The secret to a good game is to have the abusable tactics be broken/entertaining (see: MVC2 Magneto) instead of broken/tedious (see: R1 *4 in CVS1).