I suspect that evolution of Spanish tenses stopped, while being in the middle of replacement of conjugated tenses by compound tenses.
In some scenarios compound tense was adopted, in some other cases not yet.
But grammar rules, mass education/media, standardization came along; and carved the usage patterns that happened to exist at that time into "stone", preventing further evolution.
Reasons for suspicion:
I have read that around Madrid the compound past(s) are used in situations where Latin Americans would conjugate the main verb not just "haber.
In some cases, the present perfect is used differently in English vs Spanish, even though according to the respective grammar rules, there should be 1-to-1 correspondence.
That is, grammar rules attempt to explain something mostly arbitrary. Those usage patterns of the past are to some degree accidental, and do not determine the correctness of what someone says in the future. Correctness is determined by the listener, not the rules made by linguists.
Is there any evidence for or against, that evolution of tenses (or grammar in general) got stopped around 19/20th century? What about other Latin/Indo-european languages?