I’ve seen it far too many times - organisations have CMSs where they are beholden to the vendor.
Simple changes, adding a bit of JavaScript or moving a DIV, plough through a marsh-like process of define, cost, schedule, test and deliver, and it all cost money and takes far too long. The web is fast and dynamic - you can’t possibly react quickly enough, if you’re working like this.
If you are currently, or soon to be, in the unfortunate position of selecting a CMS, make sure you can answer one question: “Do we have the skills and access to make changes ourselves?”
Do not pass “Go” until you can say, “Yes”.