As someone who took a few university courses on analytic philosophy covering Russell, I've never heard anyone suggest he "sold out". Maybe that's just people who aren't really familiar with Russell or his personal life that say that?

If you're going to argue that he wrote sellout books, then he did that long before he gave up on logicism. See for example Introduction to Mathematical Philosophy, which is aimed at people who know nothing above regular public school math.

I think the ability to recognize that he had basically hit a dead end with logicism was probably his greatest success, instead of falling prey to a sunk-cost fallacy. The guy wrote one of the most influential papers in philosophy of the 20th century ("On Denoting"), as well as being one of the central figures in the founding of an entire field of study, but he knew when to call it quits, and I doubt he regretted it at all. His social and political writings and activism are a treasure trove of wisdom IMHO.

Edit: if I'm being fair though, it is pretty common for people to say History of Western Philosophy was a bit of a poor work that he did just because it would sell well. That is just one book out of hundreds of works though, and honestly it's not that bad if you balance it with more neutral sources on some of the material.