This is anecdotal, but one thing I do when comparing languages and frameworks, is browse the most popular libraries on GitHub from that ecosystem, and see how much maintenance they're getting. I usually use the contributors graph, as well as review how/when issues are handled. Ruby projects seem to have the most contributors maintaining the "deepest" libraries of any ecosystem I've seen, consistently, for the longest time. In other ecosystems I keep seeing one guy trickle-maintain some massively popular (based on stars) project that fizzled out over time. You could argue that some of that is due to "completeness", but I keep seeing evidence to the contrary: still many unsolved issues, but the initial activity spike subsides down to a trickle. To me that's what represents the health of an ecosystem: not how many new projects are created, but rather how well supported existing projects are.