The issue with Exodus can be summarised simply by saying that it took too many steps out of its niche and into the broad, generic, open-world games we've seen done a hundred times before.

It's not outright bad but it fails miserably at being a good Metro game. The world is much less interesting than the Moscow Metro (which had the chance to be fleshed out significantly in the books), and the story is so dumb that they (spoilers for Metro 2035) ran with a story and reason which Artyom pokes holes in in the book and which turns out to be a quickly-thought-up cover story for what's really going on. Not that it really matters as after the first half hour it just drops you into an "open" world, lets you waste more time walking around with nothing to do than actually doing anything interesting, then a few hours later just rinses and repeats.

If you really need your Metro fix then there are worse sequels in the world of games, but I consider Exodus to be the Fallout 4 to 2033 and LL's Fallout 3 and New Vegas - a lot of the magic is gone.