AppsThatDeliver is described as 'B2B Software Ratings and Reviews. As a 100% self-funded company, we started AppsThatDeliver with a mission to drive people and small businesses forward by presenting a hub where small businesses can get up-to-date, reliable, and solid data' and is a App Discovery Service in the Online Services category. There are more than 50 alternatives to AppsThatDeliver, not only websites but also apps for a variety of platforms, including Mac, Windows, SaaS and Linux. The best alternative is AlternativeTo, which is free. Other great sites and apps similar to AppsThatDeliver are PrivacyTools.io (Free, Open Source), Product Hunt (Free), Slant (Free) and alternative.me (Free).
When I am exploring alternatives to a product or service, I often to go Google, type "[product] vs ", and just see what it autocompletes. That usually tells me the most popular competitors. If I want to be thorough I'll do the same for the competitors, etc.