Let’s start simple: You should consider hoping from Linux Mint to LMDE if you haven’t already.
As a user, you have no obligation to participate in the politics between the Ubuntu and the Mint Development team, but if you’ve followed the controversy and agree that Ubuntu is being a bully, this would be a small yet material way to show support.
what am I missing?
Every Linux distribution has a purpose - a reason its author thought it was worth the effort of creating it. Some are grand, others are silly, etc. When you explore distros, you’re telling the community which ideas resonate with you. Popular ideas will replicate, unpopular ideas will be abandoned.
Also, switching distributions makes it harder for business to ‘capture’ the Linux demographic. The mere act of switching occasionally means that tools to import/export/manage your data stay relevant. This literally fights enshitification.
Finally, and this is a matter of personal taste, but I like trying different versions of Linux for the same reason I try different flavors of ice cream: It’s fun; and even if now and then I get a bad flavor, I feel enriched by the experience.