From what I know, their main cause is overall just and they have done good work infiltrating places with hidden cameras and recording/exposing animal cruelty...
...But their publicity stunts, probably the big thing they're known for these days, are almost always stupid and imo do more harm than good by turning potentially sympathetic people against them, and possibly by extension animal rights.
I'd argue that, at least in the case of XR, they are also somewhat successful, given that a major aim of theirs to raise awareness about climate change and show those in power that there is an opposition capable of applying pressure, and in that regard they don't need to be liked to be successful