I've seen this repeated elsewhere but I've seen zero actual evidence of it.
And the counterpoint is quite easy: that people use these apps/extensions for a better viewing experience. Because on the creation side, typing into a text box or pasting a link is just typing into a text box. The apps/extensions are great for consuming.
Quick Google searches reveal that Reddit has something between 0.5 and 1.5 billion monthly users, while the Apollo app has 1.5 million monthly users. That's nothing.
The bigger question seems to be around moderators who use power moderation tools. Will Reddit keep allowing moderation tools? If not, will they improve their own? If they lose moderators, are there other moderators willing to take their place, or will they start investing in more ML-based moderation, etc.?