As a relatively new player, I have my own perspective on this matter.
I only started playing late last year, around August-September. Plenty of the ever-necessary third-party tools and resources are still being maintained and updated, which I've used to help myself learn the ropes. Elite-related content is still being created by the players, there's a number of YouTube channels I've subscribed to and Discord servers I've gotten involved in over the past few months. The subreddit and these forums are active. Community goals are getting done, wasn't there one involving the delivery of wine for a charitable event that got smashed? Now I'm not massively experienced with MMO-type games, I think Elite might well be the first one I've ever played. But what I've just described certainly doesn't feel like a dead or a dying game to me.
I certainly wouldn't have invested as much time or effort into this game as I have if I had any strong suspicions about the long-term sustainability of the playerbase.
I wonder if the sheer size of the game world might make it a bit too easy to come away with the impression of deadness while playing, even if you never leave the bubble. Last I checked there were 19000 inhabited systems in the bubble, so if there are 4900 players at once that means 1 CMDR for every 3.8 systems. Which doesn't sound too bad a ratio until you take into account that a number of those 4900 will be outside the bubble in the first place, that they won't be distributed evenly, and further fractures like which game version is being played and whatever black magic ery is responsible for instancing.
I think that Elite Dangerous has a niche status that is both a blessing and a curse for it in terms of long-term player engagement. A blessing because I can't think of any other game which does the whole thing of allowing players to personally fly a highly customisable starship across a more or less 1:1 scale model of the Milky Way, which is the main draw of this game for me. No Man's Sky procedurally generates a wonderfully vast playground, but it's not in the galaxy I can look up and see in the real sky. Other games may be similarly impressive while still falling short of exactly what Elite provides. But this niche status is also a curse, in the sense that it means Elite Dangerous most likely won't achieve a massive boost in popularity that would provide an unquestionable financial case for FDev allocating significantly more resources towards its development. Not saying that Elite won't ever become more popular than it is now, but if it does then it will be more of an upward trend instead of a miraculous explosion.