The trick isn’t packing less clothing, it’s packing clothing that does double duty. Two pairs of pants that both go from daytime to dinner, one merino layer that doesn’t hold odor after three wears, and shoes you’re willing to wear on the plane so they don’t eat suitcase space.
I did Lisbon to Porto to Madrid, ten days, one 22-liter bag, laundry once mid-trip in a hotel sink. The only thing I regretted not bringing was a second pair of socks; everything else got used or worn more than once without anyone noticing.
Roll, don’t fold, and put shoes in first against the wheels, everything else stacks around them.