Many (most?) web projects allow hiding performance issues by scaling horizontally, caching and offloading work to native implementations where necessary (like video encoding). Python can work great in such circumstances.

The best testament to this is the reality that popular web services were able to limp along on a slow language for a long time before they had to rewrite their code.

But if one is doing something that requires raw power or precise control over resources, or precise timing then not choosing Python is not merely a tradeoff to be considered, but an obvious architecture decision.