I get the sentiments of the video. A loose amp can be tweaked and adjusted to whatever tightness you want, and in that way can be thought of as more of a "platform" upon which to build and sculpt your tone, but an amp that’s locked in from the factory to be ultra tight is basically only that and can't be tweaked any further in that regard. Also, a bit of looseness and mush can be really interesting and make for more complex shades of distortion. I agree with his points.
Personally, it's strange to me that every high gain amp on the market doesn't have a dedicated bass cut knob that cuts low end from the input. I think literally every amp with preamp distortion you can buy should have this control. Even amps built from the factory to be super tight rarely get their input bass cut curves exactly right, because an amp is just one of many components in a rig, and everybody's rig is different.
I understand that there is a widely believed trope that every guitar player in the world is a knuckle dragging retard who would immediately fill their diaper in a panic if they saw anything other than "gain, tonestack, presence, and master" knobs and that they are terrified of dialing any of those knobs outside 11:00-1:00, and I think that's nonsense. The Mesa Mark series has had an input Bass control for the last 50 years, and the latest example I can think of, the Bogner Uber Ultra, has implemented this control via its Metamorph knob and it works wonderfully.
But if I had to choose between the two extreme options presented by Fluff in his video, I'd choose a loose amp I can get surgical with, using my own tools, over an amp that's just built to be super tight from the factory and that I can't adjust from there.