https://www.pcgamer.com/metro-review-bomb-steam/

The decision to make Metro Exodus an Epic Games Store exclusive, less than three weeks before its scheduled release date, came as a tremendous surprise, especially since it had been available for preorder on Steam for months prior to the announcement. The game is actually $10 cheaper on Epic for US customers, attributed by Deep Silver CEO Klemens Kundratitz to the store's "generous revenue terms," but that discount did not mollify gamers unhappy with the move to a different storefront. 

User reviews can't be posted to the Metro Exodus page on Steam, of course, and so gamers who feel wronged are turning their attention to where they can inflict pain: its Steam-based predecessors, Metro 2033 Redux and Metro: Last Light Redux. Both pages have been heavily review-bombed over the last couple of days, and are now showing "mostly negative" recent reviews—although their overall review ratings remains "very positive."