What I think is problematic about foreclosure defense is not that it's reformist/non-revolutionary/etc. My issue is the form it often takes. Foreclosure defense usually is a cause championed by activists who act based on either a moral obligation or because they simply "want to do SOMETHING." This moralist intention bleeds through in their action, it alters how they interact with the person being defended, their neighbors, the media, or the police. This moralist, activist sentiment does not resonate with other people because they don't share the same motivating force behind their actions; they aren't interested in activism, they are looking out for themselves, their family, their friends, their neighbors, etc. So due to this foreclosure defense is limited to the activists who feel compelled to perform it.
It doesn't have to be this way though. If someone was being foreclosed on and they chose with a community of people to fight the bank and protect their home, it would be different. Their motivation would be that they didn't want to be foreclosed on, that they were sick of taking shit from the banks, that they were going to fight back against a system that is seemingly invincible, etc. This would resonate, meaning people would see their own struggles reflected in said people resisting their own foreclosure, and therefore the tactic would have the possibility of spreading. Rather than one activist group in a city who jump around defending homes from foreclosure, different pockets of people would (possibly) fight back on their own terms with their own loved ones and form their own community in their 'struggle' against the bank/cops.
What's important isn't that the tactic is 'reformist' or 'revolutionary,' but that it resonates enough to cause a rupture in how people view their relationships with the banks, the cops, 'the law,' and their obligation towards society.