I actually think Cheap Seats had much better production on the songs than Far did, but I know what you mean.
I think it's not so much that the quality of the songs has decreased - after all, many of the songs from Cheap Seats (and Far) were many years old. It's more just that the production on them is "poppier," for lack of a better term, than the original solo versions of those same songs. For example, I think Folding Chair and One More Time with Feeling are terrific songs when played solo, but I really dislike the production on the album version of both of them. It's not the songs themselves.
So I really think, for the most part, her songs are just as good as they ever were. It's just that, for whatever reason, Regina feels the need for the songs on the records to have somewhat of a glossy production... at least some of them.