so..
there are two aspects to Warhammer.. the RPG and the Fantasy Battle.
The RPG is a similar system to D&D. However the RPG system is in a weird state of limbo right now. Fantasy Flight Games was publishing all Games Workshop properties that weren't Fantasy Battle or 40K (RPGs, boxed games, card games, etc). But that is officially over in Feb 2017, and it looks like virtually everything is OOP now. No word on if Games Workshop is going to pick the RPG stuff back up.
The RPG itself is pretty solid, focused a lot on combat without trying to get as deep as DnD, but still trying to provide more than just "you hit. you don't hit". WFRP years ago used to crush DnD on skills and proficiencies and stuff.. but DnD caught up with 3e..
Beyond that, WFRP is the campaign/world.. which as others are saying, you COULD recreate in 5e if you really wanted to.. though obviously just buying the source material, which then comes with the game rules.. seems to be a no brainer.
Warhammer outside of the RPG has absolutely nothing in common with DnD. It is a tactical strategy game meant to be played with a ton of miniatures. It IS amazing.. but again, has nothing to do with your experience with DnD. If you are looking to get into it, my rec is to either pickup the Age of Sigmar starter set.. after finding a local shop to play at. If you really like what you are doing.. then look at picking up a used army off of reddit or ebay. obviously you can buy new yourself.. but then be prepared to build, paint, etc.
Personally I think the main appeal of Warhammer will always be the modeling aspect. If you are not interested in painting tons of models then don't even bother. Unpainted armies look like trash.
unpainted armies look like trash. yes. However I disagree that the main appeal is modeling. If anything, I think the fact that modeling is REQUIRED is what holds the game back. Look no further than the success of X-Wing and other CMG games.
Now the hobby IS expensive.. unquestionably. But you'd be surprised at how easy consignments can be found. I have an actual GW store in our metro area.. can usually get mini painted at tabletop quality for $4-6 per mini.