Courtois is top drawer, Szczesny not a patch on him. Come on guys, try to be objective. Rate those two on the same level in front of any neutral fan and you'll get laughed at. Szczesny isn't even a great shot stopper IMO, he's a decent keeper but nothing more.
If he doesn't improve next season it's time to consider looking for an upgrade. Neuer, Courtois, and Buffon can win you titles. Lopez, Valdes, Sirigu, Lloris, and Cech are better established keepers and De Gea, Ter Stegen, and Scuffet are better young players. That's all off the top of my head.
We have four top players in Ramsey, Özil, Alexis, and Koscielny. We need more at that level to win titles. When you have to carry all of Szczesny, Gibbs, Debuchy, Arteta, and Giroud in the starting lineup there's only so much you can hope for.