Great perspective. ESP, analytics vendors and BI tools are a few of the categories where "usage' has forced me into licenses that require annual subscriptions. Seems many of those companies do offer month to month options, but those are typically situated for low volume levels (emails/month sent, # of monthly API calls, etc.).

Personally, the biggest pain I've had is around poor implementations and core missing features that are only realized during implementation (some of my projects have had tricky technical & privacy requirements). In all those cases we either made do or spent far more time than estimated in building workarounds.