Generally speaking. The guitar cabs people find to sound the best. Are ones that are changing the sound of the speaker basically as much as is physically possible.
Mesa 4x12 have become like an industry standard. Why? 1) oversized cabs most people prefer. 2) The grill cloth are designed to be really thick and block out a bunch of higher frequencies. All the reasons are, the cabinet changing the sound of the speaker away from how it sounds if you just heard it by itself.
Ownhammer IR’s will save you so much grief.
If you are dead set on making the IR’s sound usable though, you need to apply a bunch of hi cut, I’d go down to like to at least 10k with most of the celestion IR’s. Then find a speaker impedance curve you like the most. Try ones again with more hi cut. Mesa 4x12 straight for example.