If you want to launch station segments by themselves like the Russians do the segments become more expensive, smaller, and less capable because each segment has to be its own spaceship complete with guidance, altitude and attitude control, and docking capability.
The shuttle allowed for the segments to be large, cheep, and uncomplicated. Plus the entire integrated truss system witch is quite literally the backbone of the station could not have happened without the shuttle. You would have to get your power from smaller solar arrays, which would greatly complicate the power system. Same problem with the radiators.
The shuttle did a great job with the ISS,
To bad the ISS hasn't done a great job for science or exploration. It has just been a large overpriced diplomacy tool, mostly used to keep the Russian aerospace industry alive after the collapse so they wouldn't wonder off and wind up in china or Iran.