Untitled was kind of like the love letter to blink. They knew deep down they were done, aka hearts not fully in it anymore, because of the whole Boxcar thing...Mark was permanently damaged and hurt by it, confidence & friendship shattered, Tom was done with blink's sound but still had to go out with a bang since blink was a big part of his life and where bit all started (and in retrospect ended).
They wrote some of their best work probably instinctively knowing this. Kind of like when you're breaking up with an ex (Tom) and realize you're done but you're going to miss it a bit and have that last amazing sex on the way out.
+44 was obviously Mark's heartbreak and anger from the aftermath of blink.
Neighborhoods was just forced on all accounts. Felt like it, sounds like it (still 1,000 better than Cali), DED same thing. Just bored older guys doing some music without much inspiration.
Cali is obviously not even worth diving into, it's not blink in any way shape or form other than Mark and Travis exist in it.