Hmm….
Key is above average against the run and pass and above average player overall
Tomlinson falls into the exact same boat
Jones isn’t great against the run but is a very good pass rusher
Anderson might be the best defensive player in the draft.
In what world is that not even an average DL?
Arden Key has never been more than a rotational player. Certianly he has grown into a very nice rotational player, but neither in San Francisco nor Jacksonville has he played more than half the snaps in a season. He's also undersized and not a great scheme fit. There is probably a place for him on the Bears roster, but not at the cost he will incur. I would rather just hope Trevis Gipson or Dominique Robinson develop into being a good rotational edge rusher than spend the fifty million it will cost to have Arden Key.
At the end of the day he's not a starter quality player and you are signing him with the hope that will be effective over more snaps. None of his coaches since his first year in Oakland have believed this to be the case, its not impossible but its a bad bet.
Will Anderson Jr. is a nice prospect. I am not particularly enthused by him, but I can see why some people would be. Oddly enough I think one of his more likely pro comparisons is Arden Key. I don't think he's Von Miller.
I don't like the idea of signing more than one defensive tackle this offseason. Its a non-premium position and neither Dalvin Tomlinson nor Dre'mont Jones make elite impacts on games. I would be fine with one or the other.
The cost of assembling this is a big chunk of the Bears salary cap and the first overall pick. Its not an elite group, and if Key fails to take the next step, or you see regression out of Tomlinson or Jones, or Anderson Jr. fails to live up to the expectations of his draft position its probably at best an average unit. Will everything go right? Maybe, but more likely you'll get a mixed bag of good and bad.