saying "you guys should really just make a sequel" is kinda ignorant to say to a development team ran by 3 people, its easier said than done, its also gonna put wayyy more stress on the devs.
Actually, from my experience, it takes longer to rewrite code for an existing application, it's actually less work if they made a sequel, it also gives them more flexibility to keep updating the 2nd one while they work on the sequel.
In reality, not making a sequel is what's going to screw them over in the long term. Keeping the hype train going with Among Us 2 is a better idea.
They can just release a beta version of Among Us 2 in a few months to show their progress. It doesn't take a year and a half to make a pretty decent base game. (Of course, they definitely need to update it, but they could make a decent game without spending a year and a half.