Petitions and marches do nothing other than draw attention to something, since they tend to get reported in the media, whereas otherwise they wouldn't. If over 15 million people voted to remain in the EU in the referendum it is hardly surprising that 5 million people would sign a petition to repeat their view. It doesn't exactly take a lot of effort, less than was needed to vote in the referendum. It's also not surprising that hundreds of thousands march to protest. That takes more effort but not a lot. Is marching down some London streets much harder than walking to the polling station? If it makes them happy then let them do it but don't expect it to change anything.
Tusk and Verhofstadt are politicians and they say whatever suits their political ends just like UK MPs. They are tales told by an idiot, full of sound and fury, signifying nothing.