The ACLU war chest has been over $400M the last few years, with many thousands of people in pretty much every state working with the organization in some capacity.
There's absolutely no evidence to support your claims that either the ACLU is irrelevant, nor that it has somehow shifted its momentum considerably since 2016 in what class of cases it handles (especially given the age of the organization and number of shifts vs. overall societal/cultural changes).
On the contrary, I can find many recent examples of legal actions spread headed by the ACLU across dozens of issues all over the country. If you can't find any it's because you're not looking, though you can start with their Annual Reports.
I got my impression from following the actual court cases and related news. Weird eh?
But they’re mostly irrelevant anymore - the causes they’ve started going after have a thousand other non-profits doing as much for, or better now.