They need more introductory tools/mini games that teach you the basics.

They also need regular events that bring new players in at the same time. They'll have a better time when they're matched against each other. You can't really guarantee this, but giving people maybe 1-3 "new player week" per year would raise the probability.

It's a shame they don't have time to do this before Arcane season 2. It's a shame they didn't do this years ago.

Any game has churn. If you're not bringing in new players, then you're dying.

EVE Online from 2000-2014 is the gold standard of longevity. (After that they fired their economist and ruined the economy.)