I'm sorry you're being downvoted, I see where you're coming from. The misunderstanding is that OSM is argued to be not a map but a database. The homepage at openstreetmap.org is meant to be a sort of dummy viewer, showing what data is there and that you can have different styles, it also integrates a popular geolocation service (Nominatim, this is the component you're complaining about) and some routing services. But it's all just a demo and not meant to be the best one could offer. There is no proper user testing because it's not a commercial company and also because it's just a simple demo, similar to how one might have a demo for some JavaScript library that shows many or all of its features but not necessarily in the best or most integrated way.

The idea is that this database can be used by anyone, e.g. OsmAnd, the openstreetmap.org homepage, Facebook, Apple Maps, Mapbox, GraphHopper, etc. provide various services on top of it. Nominatim, the component you're having trouble with, is indeed fairly picky in its input.

But do mind that you're comparing this to Google, the company on this planet that is the undisputed king of search. I'm not surprised their search function works better than this open source project using an open source set of data. For what it's worth, if you stick to common address formats and don't put in abbreviations like a country-specific postal code (it doesn't look for results near you, it just searches the planet for what you typed; it has no knowledge of where in the world you are as it doesn't track you -- yeah, maybe it should), then it works fine, or at least as reliable as the underlying data is.