This game has already turned into an ultimate slot machine. The only thing we can do in the game is searching for the same gears from a rain of trash drops.
The development team has lost all creativity. I can even predict the theme of the next season: Legendary gear can also become Mythic, but the Aspects will be random and cannot be imprinted.
This isn’t New.. “we” have been doing that since season 1.
I dare say most ARPG do this to a greater/less extent anyway. 
And the season mechanic is going to be construct a pet using stones to customize skills.
Is this like the Diablo version of “wow is dying” that we’ve been hearing for 20+ years?
I believe so too
However, they need at minimum 6 good seasons to cycle through before they can fully go into Maintenance mode.
So we have some time.
I expect them to rerun unpopular seasonal mechanics again like they did in Season 14 to try and salvage the old seasons since it’s less assets intensive than making a new season from scratch.