yeah im a Bart maximalist, like I think virtually all of the transit in the bay should gradually be collected under the bart umbrella. Bart and Caltrain are complementary. Bart + bus connects quickly to ACE at Centerville, most of BART lies in the AC transit footprint, and BART+ GG transit + SMART would connect Santa Rosa to the bay very efficiently
And like if BART+ACE get coordinated it would connect SF to the HSR IOS like a decade before it connects to the transbay center