You explain what the website does not but so much what problem is being solved. I use alternativeto a lot, and never had an issue finding what I need. I usually type the name of an app related to what I need and browse the alternatives. Usually I'd also select a few filters, for example the operating system or open source.

At not point did I think "I can't do x or y, and if only there was a similarity index or robots I could". So you might have more features than alternativeto but why would anyone need them is the part that's missing.