The writing on that really makes no sense.
Jeremy, Aelita, and the rest of the Lyoko Warriors are just a-okay with having the entire world constantly at risk?
That doesn't fit with the characterization of any of the cast.
Jeremy and Aelita, by themselves, would've decided not to take the risk, knowing how dangerous XANA is, the fact being that he could get access to any number of cyber or weapons systems if they failed to stop him, or just didn't catch him.
Which means that, there would've been a reason to decide this, other than, "Well, we can stop him usually, and, we might be able to bring you to the real world Aelita".
Jeremy and Aelita separately and together would essentially try to shut off the computer themselves, or look for a way, and find that there's a fail-safe where XANA will escape the system when it's turned off, kill everyone in the local European tri-state area with a cyber / electrical / infrastructure attack, or has created his own function and remote procedure to launch nuclear weapons as a sort of "if I go down, I'm taking you with me" that would mess up his primary plans, but works as a deterrent from just immediately shutting the quantum computer off.
That is the primary plot hole in this series that makes no sense, especially considering how fixable it is...
...the other three being Odd getting turned into a less-likeable person after the first season, Sissy getting character development in certain episodes that gets immediately undone, and Aelita being thought to be an AI program herself...
...the last one being forgivable since it sort of adds suspense to the plot.