I'm not sure it's entirely impossible to be a small player.
Let's say, a small player allows their users to make a copyright statement with the "proof of original content" (not necessarily 100% valid, just something like "I, Max Mustermann, confirm that this work is my original content produced on 13.09 in Berlin..."), possibly, automatically. This statement will identify copyright holder of the content and mark it valid, since copyright holder himself uploaded the content. This may (but not necessarily will) mean that other filters/copyright checks may not be executed, because the platform allows the participation only of original content creators.
One more option (assuming that the national law will take amendment 149 into account) is to implement a filter as an API call to the server designated by the right holder and expect the claim/"no infringement" response with some reasonable timeout (1 sec) and detailed response in extended time frame (10 min). It's a cheap "now it's your problem" solution, that might actually be allowed.