The most fun there was to be had in this game was the original Adventures. It was an interesting and very replayable PvE game mode where you ramp up power over time by fighting battles around the map (on an energy system—it wasn't too bad) and take on the elites and zone boss. It was straight-forward, it was (modestly) rewarding, you could play it on top of PvP, and there hasn't been anything like it since.
You really never know what's different about a game until you reinstall it, and I came back to tons of chests to open. The new "Adventure Mode" is an awkward Slay the Spirelike mode, and as expected, losing kicks you out. There's no explanation of how it works, whether you can repeat it, and only one of them is free. At its core, it's still just the same PvP game it always was, but it was advertised as having (or at first, desiring) robust PvE content, and it just never got there.
Even from a PvP perspective, there really aren't as many cards as there ought to be for a game in development this long. I remember making a Skeleton reanimation deck around launch, and it was so terrible at doing anything, it wasn't worth engaging with the PvP content at all. The game isn't quite casual enough to just play and not worry about getting something out of it. Menus and UI elements are a mess. You can't replay the tutorial. You've already missed all the FOMO cosmetics. Many of the cards and mechanics are fun, but there's no hook.