negative feedback causes micro transients to be subtly altered and smeared. this can give false cues as to soundstage and detail information. like the exaggerated beauty of breast implants collagen lips and oversized butts. that ain't beauty, it's exaggeration for those with blunt senses. (this is why the best in mediocre audio gear is confused by the audiophile masses as being 'the best', when it is clearly not and those middle quality 'imagined as the best' brands make all the money, like the fake beauty with the breast implants. the best will ALWAYS be in the places you currently don't understand. until the day you die, and afterward - this will remain true)
after a while (high negative feedback amplifiers) it becomes aurally tiring and painful, even. It takes time and is also tied to human intelligence and cognition speed, over time. hearing is the same, in that way.
some get it, some never will. Heresy’s don’t really deliver a deep wide sound stage and never will. You were more listening to false edgy cues.
what the tube amp did, to some degree, is illustrate that, clearly. the trick is working one’s way through the inordinately complex logic and data and understanding about ears and gear, in order to ’see it’.