Aeropress coffee is great but it's not really the right answer to 'how can I make nicer coffee than with my cafetiere and pre-ground coffee combo'.
It's as much a right answer as suggesting buying a grinder is. Why replace one half of the combo but not the other?
The OP asked how to make nicer coffee, not how to make nicer coffee only via cafetiere... they also said they'd be willing to invest in some stuff. The aeropress is one bit of stuff that'd be worth investing in for sure, as well as a grinder.
It's as much a right answer as suggesting buying a grinder is. Why replace one half of the combo but not the other?
The OP asked how to make nicer coffee, not how to make nicer coffee only via cafetiere... they also said they'd be willing to invest in some stuff. The aeropress is one bit of stuff that'd be worth investing in for sure, as well as a grinder.