They're weak because their candidates are weak and not serious leaders. They come across as single issue voters running for office. Or as environmental student graduates who couldn't find a job and are padding their resume.
They're also incredibly partisan. Like good luck convincing a Green candidate to endorse an NDP candidate who might have a chance of flipping a CPC incumbent. And I know someone is gonna reply to this with their tired tirade, "Expecting GReen voters to sacrifice their prinicples blah blah BLAHHHHHH."
I want better environmental policy. But the green party isn't capable of getting us there. Their candidates have no vision beyond themselves standing at a podium hearing the sound of their own voice. They have no plan to accomplish their platform and nobody interested in working with them either.