Nothing.
If that's what floats your boat.
And if the new version in Debian angers you enough, you have two choices, both of which will allow you to keep the good old FVWM that you love:
1. Fork it at a point where you deem that you liked it
1a. Compile a debian package sans GNOME integration
2. Pin the package at a suitable version
(2) is less work than (1a) is less work than (a), but all are work; this is what happens when the developers of a package exercise their right to take the package in the direction they want.
