The major reason the Gra signed the letter of excommunication clearly is because of the problem with idolatry. The problem with worshiping a corpse is certainly no worse than worshiping a statue.

And just because people put on black clothing is that supposed to imply that somehow or other that is equivalent to keeping the holy Torah? Or supposed to make them smarter or superior to others?
So we can surely see the Gra was right  and it is about time to start paying attention even though it is a bit late. Better late than never. The reason is the effects of ignoring idolatry is still with us.
And it is not just idolatry. Worship of the Sitra achra [Dark Side] is surely a more severe kind of idolatry.