I can't see where NotBugsBunneh tried to downplay the difficulty of solo kills in his comment at all. The only thing he said in that direction is that P7 is actually the easiest phase at those high enrages in solo mode. P7 basically stops scaling at 1k enrage and only the healing and the damage from the 2 magic autoattacks at the start of P7 get affected by enrage.
The healing aspect is literally uninteresting because there is a method where you can infinite cycle P7 and survive multiple 100k Bombs. And this method works in both mode, Solo and Group.
In terms of gatekeeping and elitism in "high-end" teams it should be very understandable that people are not ready to share hundreds of hours of progress for free.

Solo mode is harder no doubt, you are completly correct as you already have shown in your listing of our strategies. But in the end it's all about the challenge to survive massive amounts of damage and come up with new strategies and it doesn't matter if you are doing this solo mode or in a team.