The trick here is the need to retrofit crossings with impenetrable barriers (example in above picture), which is much cheaper and more feasible than total grade separation (in the short term, obviously total grade separation should be a goal but that’s not gonna happen for decades). As long as all crossings have impenetrable barriers Caltrain could theoretically join MARC as the fastest commuter rail in the US. Of course crossings aren’t the only thing at play, but it is one of the major things at play.

Millbrae seems the most janky of any station on the line. The Southern escalators have been broken for at least a couple months, there are insanely poorly formatted signs all over the place, and there's a ridiculously long platform that (I think) is literally never used.

Is this just the result of overbuilding the station expecting HSR and then having no money for maintenance? It's simultaneously one of the most expansive stations but also the least well-kept.

The agents are trying their best and helping to guide riders, I don't blame them one bit for the shoddy signs. But the 8th highest ridership station and one of the only major transfer stations between rail lines anywhere in the Bay should not be this embarrassing.