I couldn't buy VTSAX through them but I could buy VOO.
It'd be great if they'd allow VTSAX recurring purchases without any transaction fee, but looks like you can only do it for their own mutual funds. And yea, you can always just buy ETFs like VTI, VOO, BND instead.
I assume you mean Merrill Edge instead of Merrill Lynch brick and mortar locations with advisors. This page has a comparison of Vanguard equivalents https://www.bogleheads.org/wiki/Merrill_Edge