Value drift towards the right values (i.e. Effective Altruism) is good, value drift away from them is bad. Value drift among EAs is likely to be a bad thing due to regression to the mean. We can imagine better values within EA, but there’s no reason to expect value drift to go in the right direction. Of course we can identify better values and promote them among EAs, but that seems notably distinct from value drift.
On the other hand, we can imagine people with bad values who should regress to the mean, and would encourage value drift there.