Of course it's too early to gain perspective, but you are trying to make said perspective on one game.
The discussion around Richarlison is also not so much, will we miss him, but more how much will we miss him given the replacements we ate getting.
We didnt lose that game because of Richarlison though. We lost because a dubious penalty was given, and I'm really sorry but if you think that was a free kick in Sterling in the build up, you really dont know about football mate. I can see a world where the pen is given, but you cant get free kicks for slipping over.
I'm also not sure what you mean by Tarkowski being too tight. He is stood off Sterling. You can see he stops and doesnt even touch Sterling as he slips. If you're saying defenders cant defend like that, you're essentially saying you can defend at all, as if you are stoid within 2 metres of an attacker it's a foul.
But alas, I'm not sure 1 game, against a substantially better team is really enough to judge we will fatally miss Richarlison. We probably missed a fully fit DCL more. As someone who watches us most weeks though, the shape, defensive organisation, and set peice defending was a lot better than last year with Richarlison