I had a roommate once that didn't pay her rent before moving out. Sued her and she got several letters, including the invitation to the court date. She ignored them. Default ruling in my favour, they seized €900 from her bank account.

So yeah, some threats are quite real without the cops having to show up.

Thats not correct. Abmahnungen need to be actively dealt with. Ignoring them is not enough. While you do not necessarily need an attorney it is highly adviced to let someone write the letter for you.

Some random source for some infos: https://anwalts-atlas.de/was-passiert-wirklich-wenn-man-eine-abmahnung-ignorieren-sollte/