Anything that requires some kind of SEO is a dumb idea for a SPA. If you're making Jira or something, a SPA makes sense. The issue is, the bovine tech herd sees new thing and applies new thing to everything. Everything is React now. Now we have news websites as SPAs, the worst possible use case for a SPA.

My side project is a web-based music video creator. It literally could not exist except as a SPA.

IMO:

- SPAs make sense for "applications". Google docs, Gmail, Trello, Slack, web-based music video creators, etc. Things that need high levels of interactivity. - SPAs don't make sense for "websites". Blogs, forums, search engines, news sites, etc.

Of course, many things exist somewhere on the continuum between "website" and "application", and then the tradeoffs get messier.

Gmail arguably doesn't need a high level of interactivity - that's why they also have the basic HTML version.