The worlds they inhabit may be a bit off, and there's a deep...sigh...hipster quality running through it all. But they are all heartbreakingly sincere from Rushmore on...

Max and Herman surrogate father/son relationship.
As quirky as the Tannenbaums were, the regressed childhoods of all the characters were pretty dark up until it climaxed with the attempted suicide.
Life Aquatic was him at his most cartoon, and he balanced that out with fucking Darjeeling Unlimited which was probably TOO sincere, lol.