I think the problem is that philosophy has, as a field, done a shockingly bad job of evicting obsolete and incorrect ideas (not just useless ones).

Totally agree.

Someone who seeks a philosophy degree can expect to waste most of their time and potential on garbage.

Not exactly. The subfields are more than specialized enough to make it pretty easy to avoid garbage. Once you're in the field it isn't hard to locate the good stuff. For institutional and political reasons the sane philosophers tend to ignore the insane philosophers and vice versa, with just the occasional flare up. It is a problem.

It's the only reference class I know of for philosophy writings that's (a) larger than one author, (b) mostly sane, and (c) enumerable by someone who isn't an expert.

Er, I suspect the majority of "naturalistic philosophy in the analytic tradition" would meet the sanity waterline of Less Wrong, particularly the sub-fields of epistemology and philosophy of science.