If reaching the end goal is the bar then the Civil Rights Movement was a spectacular failure, because they didn't. The Movement didn't achieve equality, not even close, but it was a success still because they achieved a lot. Of course Insulate Britain can't be compared in scope, but it's a success if more homes are insulated.
I can make a comparison in a completely different direction. Over here we have an anti-Muslim group that regularly protests. Their end goal varies, for most it's a complete stop to Muslim immigration, for a lot it involves deportations, and for a sizable bunch it's not really about religion but about colour. They won't reach that goal, and they're seen as pathetic people by most. What they do achieve, however, is to help keep people talking about Muslim immigration. They're pretty damn effective for such a small and loathed group, even if what they achieve is just to draw some votes to the right and get people to harass Muslims rather than the deportations and killings they want.
And being disruptive is a fundamental part of protests. I'm very surprised you're questioning this. You don't think the marches from Selma to Montgomery stopped a lot of traffic and made it more difficult to go to work?