Reasons to play the original Hellcore
There are some, as it turns out.*
If you like Alien Vendetta, in particular maps 12-14 of it, then Map18 of the original Hellcore is basically another in the same style by the same author. A cousin, if you will. Not quite a brother, it's been a bit mashed with the detail stick, but nonetheless.
Map19, the original version of Baron Streets, is better. It's not totally linear, and you can actually kill the monsters!
The "old shame" levels - as opposed to graphic demos / attempts to recreate other newer games in (a limit-extended, "more forgiving") Doom engine - are actually complete and quite playable, if you like nineties maps. Although they tend to disjointness, long corridors, and require multiple traversals. So, a bit tedious. But, a lower monster density. Not frustrating by being killed all the time and having to restart.
* I never bothered with the original release at the time in 2004. Then after a couple of years a stripped down best-of mapset came out, which I talked about at some length. Last month the original release was mentioned on the front page of Doomworld. On a whim I downloaded it again.