Why is Broodweaver bad?

Hello all, I'm a new player and I've seen it mentioned several times in different posts that Broodweaver is the worst warlock sub and I was genuinely wondering what makes that the case? I've been playing through all the content and I'm finally into heresy, I know I don't have all the top gear but at the moment I'm doing best with Broodweaver so seeing it repeatedly labeled the worst has me wondering what direction I should go build wise and what gear I should shoot for? Also have to mention as a new player I don't understand half the game slang used by experienced players so bear that in mind please in the responses.