I've never used packing cubes, and I don't regret it.
But then, I don't use many Ziploc bags, and I don't use the ones I do as a substitute for packing cubes either. I carry one Ziploc bag (not 2½ gal) for all the paper records - rail tickets, restaurant receipts, etc - I accumulate over the trip. The other bag I hardly ever use; it's just there in case I have to travel on a day when my hand wash is not dry by morning (so far it's never happened, but I have the plastic bag to put damp clothes in, just in case). I can also use it to hold dirty clothes if I don't have a chance to wash the night before traveling.
That doesn't mean that I'm not a proponent of organized packing (putting clothes in individual packages that can be easily unpacked and packed), but I'm not a "packing hog". I've learned to pack light, and I take advantage of it. Half of what I take with me to Europe for 2-3 weeks would fit in one packing cube - their size is overkill for me. I use a variety of smaller, mostly mesh, containers. I have a small mesh bag that I got with something from RS, for my underwear, a larger, flat Tide wash bag for my folded shirts, and a nylon stuff bag for my electronics. I find it more convenient to use my travel bag as the container for my slacks, folded, first in, on the bottom. My "toiletries" are already in a case that I hang up in the bathroom.
Hotel rooms tend to be small in Europe with not a lot of space for storage.
if I packed them full and tight with clothes, they tended to break
Both comments indicate you are trying to pack too much. As do the comments about trying to push out all of the air (note: this decreases the volume, but not the weight).