The issue (at least my issue and my rabbi’s issue) with YCT is that their psakim are not informed by any kind of standard halakhic process as historically practiced by poskim. To be fair, this issue is present in many other camps, but YCT is more egregious than most because they loudly proclaim “b’shita” that extra-halakhic considerations justify the way they “push the envelope” and that those considerations in fact trump normative halakha (while at the same time carefully staying within the bounds of muttar — barely).
That pretty much sums up modern orthodoxy in general, not just the “left-wing modern orthodoxy” of YCT.