I think the point is, if you dont like the taste of steak, don't buy one and try to make it into a pork sandwich.
When I boost an amp, I am trying to bring out more of the character I love about it. And obviously tighten it. I am not boosting an amp to completely change its character, otherwise I go with an amp that has more of that base and try to improve that.
Some people like boosting marshalls, others tweak a marshall circuit to bring out more of the characteristics they like within the circuit.
If I bought a recto trying to make it sound like a line 6, I would be making things way too difficult.
You dont have to buy a Larry or Wizard if you want a fuzzy sound. You buy them for the clarity, punch, immediacy, and tone. You buy them so you can play a complex chord and hear all the notes clearly. If you can dial in a fuzzy doom sludge tone to where you can clearly hear the notes of a chord, then you have serious skill. It is the exact opposite sound I would go for, and the opposite sound those amps go for.
f you don't care for that tone, nbd. But to say you don't need those amps because you can make a Marshall sound like a distortion pedal, it is a little strange. Those amps were never trying to be that.
Realistically even a jcm 800 is kind of a roundabout way to get to that tone.