A protest with enough people is important whether anyone is inconvenienced or not. For example, the women's march.
Inconveniencing people is a tactic for those who don't have numbers--and it's not a good tactic even then because it gets hostility rather than support.
The complete shutting down of the surrounding area of Trump Tower inconvenienced no one???
What if instead of clogging all of Manhattan (and many other cities around the world), there was just a petition circulated that collected millions of signatures? would that have had the same media coverage and impact, in your opinion?
The thing is the politicians listen a lot more to numbers than to inconvenience.