Yes, snapshotting is what allowed the dot specs to shine, and gave them very interesting and fun ways to change the gameplay via trinkets or just any proc/active/on-use in general.
Since it was removed feral has been on an identity crisis sucking ass and affliction/shadow had to be changed 20 times because it was hard to balance them.
MoP was the golden age of snapshotting, and it was also removed on WoD pre-patch.
Examples of trinkets completely changing how you play your spec:
https://www.wowhead.com/item=94532/r...re-origination
https://www.wowhead.com/item=94524/u...on-of-lei-shen
Allowed demo locks to maintain a 100% crit doom and it did bad things to the boss.
Currently feral does have some snapshotting with 2 abilities but it's baby stuff compared to before. (TF and Bloodtalons) but stats do not snapshot.