The thing is it is less of an antitrust concern for two also-rans in an industry to merge than it is for the industry leader to buy a struggling competitor. People don’t like the politics of Paramount’s ownership but from a competition perspective this is the better outcome.
We’re talking about multiple industries here. In streaming Netflix is dominant. In terms of movie production studio Netflix is the also-ran compared to Warner and Paramount.
A purchase by Netflix would give them something they currently do not have. A purchase by Paramount is a much more direct merge of two competitors.