If a fancy new feature can’t degrade gracefully, then 98% isn’t “widely supported”.

Close, but the other way round. Don't avoid a feature because it lacks good enough support. Write code to progressively enhance the experience if the feature is supported in the user's browser. If you're not willing to do that, then don't use the feature.

Progressive enhancement today means you can use pretty much any browser feature you want. You just have to do a bit of legwork with some @supports or JS prototype checking after doing the basic version first. It's not really much extra work.