The problem with learning plugins isn't a shortage of material: there's a ninety-minute tutorial for every compressor in existence. The problem is that you watch the video, follow what it says, and then open your session still not knowing which of your eight installed compressors to reach for.
Plugin Quest inverts the format. Instead of explaining a plugin and hoping you remember it, it puts a problem in front of you and makes you choose between specific tools. You get it wrong, you see why, and next time the association is already made. It's the difference between knowing what an 1176 is and knowing when to reach for one.
Before the specific classics there are family cards: what a compressor does, an EQ, a reverb, a saturator. That order is deliberate. Learning that the LA-2A is a slow optical compressor is worth nothing if you're not yet clear on what problem compression solves. Once you have the family, each individual plugin is just a character within it.
The reasoning behind the two hardest families is in the guides to compression and EQ. To practise the whole decision on a real problem, mix diagnosis.