I think two things happened over Lambda's life span that effected the quality of the teaching. The first was the initial pool they advertised too. I think I saw the post on Hacker News before everywhere else. I'd wonder if you're more selective from already technical people at the beginning and then sorta widening the net as time goes on to include more people if you could get initial big numbers push followed by more ok numbers.
The instructors I met were all great. I think a lot of that flack went more towards later cohorts or alternative program from the main full webstack track.