I don't think there is or ever will be a "new internet explorer". If your page works in Chrome, there's a 99% chance it'll work in Firefox and Safari. Web standards have been unified to the point painting and layout algorithms are now part of the spec. It's why Ladybird managed to get a decently compatible engine in an extremely short time frame.
To make an obviously unproven and not universal observation: I feel like it's people who just like the google integration in Chrome and want an excuse to run it, even though they feel like they should use Firefox because it's more compatible with their world view, so they latch onto any issues Firefox has to go "see, they are all the same anyway", and then just repeat vague "Mozilla sucks" stuff.
What world view is this? Considering that Mozilla is a puppet Google basically owns if you look at where the funding comes from.