I never thought of the thumbs-up as meaning "like", but rather "agree". So of course there should absolutely be a thumbs-down, i.e. "disagree".
I'd also get a lot of use out of a new jiggly-eyed reaction emoji, translated as "just plain nuts!"
Ignore? I ignore (lower-case i) any number of people...meaning that I just don't bother paying attention or listening to them. But I'll be damned if some internet a-hole will ever influence me enough to actually press a special button to protect myself from them, i.e. Ignore them.
But, IMHO, the most-needed new reaction emoji is a confused wide-eyed one, intended to translate into "what the **** are you babbling about now?" I'd need a keyboard shortcut for that one.