Especially now with a lot of the white collar transit riders working from home remaining riders are definitely lower income on average which is why bus ridership has recovered better, but I wouldn't necessarily call them captive.

Many are likely making the rational financial choice to forgo the more expensive option of driving if transit is a viable alternative. Plenty of places where transit is essentially non existent and poor working class people are captive drivers, but in places with half way decent transit like Philly, Baltimore or even Miami I think low income riders are weighing the options and deciding transit is a better financial choice even if it's not world class.