Necro is fun, but do not expect it to be like in D2/D3. In general, the game is a bit slower paced and more challenging, depending on the classes/builds.

PoE is far more complex when it comes to the skill tree and item crafting. So if you managed to get along in PoE, perhaps followed some guides, you'll be fine in D4. If you like theory crafting and creating your own builds, D4 starts to get interesting with the paragon boards. If not, grab some guides from maxroll.gg or similar.

Compared to D2:R there is no essential need to farm for uniques, which was sometimes driving me crazy. Some builds do really shine with uniques, but you'll be fine without any.

As of mtx, it's not that bad... there is no need to purchase anything, and the unlockable visuals by salvaging drops are quite nice. In fact, at this time I do not think that mtx cosmetics are really worth it.

In addition, you can find horses and horse visuals as random drops even in world tier 1. One of the coolest horses (imho) happens to be found in the Legion events.

what I find annoying sometimes is that some quality of life features they developed in D3/D2, were not taken into account in D4. Why not take some of the things they learned over the years and put them into the game? (e.g. build saving, respec paragon all at once, gold/resource pickup pet, ...)