ACLU membership and staff have always been fairly left, but they were impressively focused on (IMO) the most important civil rights as rights through their work at ACLU, and largely kept their personal politics out of that. A "mission driven organization", as it were. Pretty sad to see what's happened over the past few decades (accelerating; not sure when it started, but it got really bad around 2012-2016, and then far worse). They always believed in "all civil rights except 2A", but I could overlook that since there are other 2A-specific organizations.
I still support them on specific issues, but they're often on the anti-liberty side on other issues, or just actually crazy. Sad.