The middle ages being incredibly gross is a misunderstanding that goes back to the nineteenth century. In that era cities were overcrowded and very filthy and they concluded that in the 'dark ages' this would have been much worse.

It gets perpetuated by Hollywood always having someone have excrement out of a window or peeing in the street. Yet those were collected for fertilizer and as washing purposes (urine contains ammonia which is handy for degreasing wool).

Another common myth that keeps getting related is that people drank beer as the water was filthy. Water is the main ingredient in beer and people did know boiling water purified it.

Would it smell like roses? No not at all, nor does it in modern cities. There were stupid and filthy people, just like today, but usually people did make an effort of keeping clean.

But if you want really filthy cities, you have to go to the nineteenth century, where human waste was combined with a lovely dose of unbridled industrial pollution.