Up until the early 2000s I used to compile my own kernel, carefully selecting only the options that I needed.
Then I realised that I wasn’t saving memory, because almost everything was a module anyway.
Is there any actual benefit to using a custom kernel on consumer hardware that’s supported by the stock kernels?
Not really unless you need a specific optimization or module that isn’t available otherwise. Most distros make distribution of external modules available via package manager, and most of the optimizations you would want to enabke can be turns on or off elsewhere as feature flags.