It's a fake issue.
By that logic D&D is also 600 pages, because the PF2 core is the equivalent of the PHB and DMG combined (possibly also the MM but I don't think so).
So why would that issue need to be addressed?
The basic rules you need to learn to get playing are highly comparable to 5E. If you can handle 5E, you can handle PF2. It's also a laughably bad example because it's one of like two games slightly more complex than D&D 5E.
Because there is a sizeable community that has already learned 5e, and would need a reason to shift.
I think you have it backwards. The OGL lead to system dominance because 3PP could just support D&D instead of creating something new. It's literally the network effect. So the industry almost as a whole directs their efforts to supporting D&D. Even those few who's main drive and passion is other games...they still have to produce 5E content because they need the money to keep the lights on and the paychecks from bouncing.
There's for sure a chicken and egg thing here, and I agree the OGL mattered, a lot, but I'm talking about today, right now, going forward.
If "the industry almost as a whole directs their efforts to supporting D&D" and we take "D&D" to being 5e, or 5e-alike rule sets, and even if some are doing it while holding their nose to keep the lights on, this kind of proves my point.
I'm not saying there are no other systems.
I'm not saying there are not BETTER systems. (I've been pretty open in my disdain for 5e!)
I'm not saying there are not BETTER companies to support. (I've been extremely open in how I feel about Wizards.)
I get it, there are other games out there and folks wish they would be played. Please, everyone come to your senses and realize that PF1 is actually the light and the way!
Failing that happening, what I have been thinking about is 'can we please more people' by accepting 5e as a base, and building upon it, with a 5e-alike, but offering enough change, and accent on the shared language, to INCREASE adoption of our version of the game, while still feeding off of, and into, the 5e ecosystem?
Its what I would imagine, Black Flag is doing honestly.