Also, concerns about the long term (decades+) results of fixing similar issue by only splicing new genes in.
Nature exploits opportunities. If we're still planting monocultures of cloned plants (plus whatever genes), that's still going to be enticing prey. See: Roundup resistant weeds.
I'm not sure that fungus gains anything evolutionarily meaningful from learning to infect this particular banana.
The only thing you get from this is annoying humans, which doesn't sound a very good evolutionary strategy (second only to being used in Chinese traditional medicine)
Nature exploits opportunities. If we're still planting monocultures of cloned plants (plus whatever genes), that's still going to be enticing prey. See: Roundup resistant weeds.
And life, as they say, finds a way.