OpenXcom has this, plus a lot of other improvements and bug-fixes. I'm no expert (played it and the original for a few hours each about a year ago) but my impression is that it manages to pull off nice QoL-improvements while staying faithful to the feel and gameplay of the original game.
I know that there are also some total conversion like Piratez XCOM.
I tried to love the firaxis XCOMs. They kind of scratch the same itch and I appreciate not to have to manage bullets in the inventory but some of the simplified mechanics just don't work that well.
Clusters of enemies in particular seems like very poor design to me. It has caused tons of issues in their 2 games, from encouraging turtling as a the main dominant strategy to forcing firaxis to add timers to try to force players out of the play style their game made dominant.