Progression literally means progression. It is all about content. Rewards have literally nothing to do with it. Mage Tower is solo oriented content, though it doesn't have any direct progression to it. It's a one-and-done kind of thing with no real reason to do the repeated content if you've already obtained the reward.
Brawlers Guild is actually progression content, but it's capped and limited.
None of what was said was about obtaining the Best Rewards. It merely is about having the content and having the rewards to sustain solo-play, whatever form that may be.
It's already difficult enough to push a point on making people realize that solo-oriented content already exists in the game. There's really no reason for us to have to go through this absolute circle just to recognize that it already exists just so we can move on to talking about something more.
Let's be frank - no matter how much solo-oriented content Blizzard makes, there will always be Raid and Mythic Plus content. That doesn't go away just because something else gets increased. I'm honestly not sure why this seems so threatening to you. It isn't a give and take any more than PVP merely existing is a threat to all PVE, or LFR existing being a threat to all Normal+ Raiding like people thought it would have been back when it was first introduced (and many years following). Whatever effort they put into it is really no different than the effort they put into making more quests between major content patches. None of this threatens Group-based PVE content.