People say this, but I've never really been vexed by the apps they provide until relatively recently. I'd like the interface to be speedier, for example.
The biggest gripe that I've understood from other people is around classical metadata, which I agree iTunes and Apple Music have done a bad job with, just like most every other service that doesn't focus on classical. I'm not a big consumer of classical, so it doesn't bother me very much, but I can see how it would be a BIG deal for people who listen to exclusively or mostly classical recordings.
OTOH, I'm encouraged that there exist niche services that focus on the classical market. I hadn't heard of this one, but in one of my periodic attempts to Listen To More Classical I had a subscription to Idagio for a while, and found it generally pretty great.