No, you are disappointed that Mastadon doesn’t have the same feature set as Twitter. The fact that you can search off instance at all is impressive. What you are asking for is like saying you should find GM cars in Ford’s search bar. Each instance is its own website. Search engines are designed to do what you want, and as Mastadon grows in popularity, it’s search results will become more prominent.
I’m not talking about interactions between instances, I’m talking about Google and Bing indexing Mastadon. That’s who we should be using for search.