A high frequency schedule gives passengers confidence in their ability to make a following train in the event they miss their connection.
Yes indeed. Only a high frequency can guarantee connections without risking holding up the trains that provide the guaranteed connection.
you couldn't slow it down any more if you filled the streets with molasses
Of course we know this is not literally true, because it has been tried, and it did slow the traffic down more.
But your point is well taken.
On the idea of connecting POR and NYP via Worcester without Boston, conflicting thoughts: On the one hand, taking one or two of five or six daily trains away from the biggest city on their current successful route in order to get a more direct route to a city several hours away would be foolish even if the tracks were already there and already maintained and signaled for 90 mph. On the other hand, Lawrence-Lowell-etc.-Worcester-points beyond to Providence or Springfield
would be a good route to have in a future in which a web of frequent trains and easy bus connections covered SE New England; in that future, a running a couple additional Portland trains around the circumference of Greater Boston, or having some Portland trains connect with circumferential trains at Lawrence, or some such, would kind of make sense.