Looks like the website is implementing a specification that clearly states “not ready for implementation” causing OSM breaking in some browsers (see: More umap (openstreetmap) problems - Pale Moon forum ).
Should functionality be sacrificed for FOMO?
This is umap specific, maybe you want to ask umap developers?
Maybe not with this phrasing though - it’s unlikely to make anyone want to help you
For others’ context, it looks like this person is talking about uMap using an experimental web animation API, not OpenStreetMap itself.
The Web Animations API (getAnimations()) has been supported by almost all browsers since around 2020:
https://caniuse.com/web-animatio
https://developer.mozilla.org/en-US/docs/Web/API/Element/getAnimations
It also looks like the last time an issue was reported to the umap project from the pale moon user, it was taken seriously and fixed instead of just being told the browser wasn’t supported (which, honestly, would have been a fair response).
I suspect this time they might just say that since the Web Animations API is widely supported they won’t be changing it (and pale moon should implement it instead), but then you’d have recourse with the W3C Enforcement Unit which should be your next escalation.
or w3.org docs should be changed to indicate that they failed to make implementation-ready version of specs so browser-makers decided on their own
though passive-aggressive tantrums should be avoided also there (and phrasing in this post is too passive-aggressive to use as-is and is not an implementation-ready version)