KSP's stock career mode does have missions involving retrieving individual pieces of debris. Though it's not framed or incentivized as "removing space junk" in

KSP's stock career mode does have missions involving retrieving individual pieces of debris. Though it's not framed or incentivized as "removing space junk" in exactly the way you mean. There's also an anime series about space junk, 'Planetes' (https://en.wikipedia.org/wiki/Planetes https://en.wikipedia.org/wiki/Planetes) -- which does the best job I've seen in any visual media of getting orbital mechanics right, and is generally somewhere between 'The Expanse' and 'Seveneves' on the scale of sci-fi "hardness". And, as far as anime goes, is relatively light enough on "anime bullshit" to be watchable even if you're normally not into that.