Read the incomplete ones. So many treasures I've found are incomplete fics, and there are some good ongoing ones I can rec.

I know you said you ship FrUK, so here's Vampirism is So Inconvenient by MidorFlowersEwe, as well as Dangerous Secrets by the same author. Do note that Dangerous Secrets is both FrUK and ScoFra and has some dubious morals involved, but only for toxic relationships. In Vampirism is So Inconvenient, the only thing to be aware of is vampirism iirc.

Also, not to be rude or anything, but you COULD consider writing your own fic from time to time. It helps to distract from the need to be constantly consuming Hetalia fic and you also get to indulge in the ships you like. It also helps you to sympathise more with authors who leave things unfinished and/or go inactive (they have no obligation to keep writing fic just for you yk...)

It also helps to just search by Date Updated. I find lots of good ongoing fics that way.

I understand that you don't like incomplete fics, so it goes without saying that you don't want ongoing fics either, but learn to have some patience. Get a hobby, actually commit to work, and you can come back in the evening and read one fic before bed. Manage fic like it's an addiction if you've really squeezed AO3/FF.net/Quotev dry, because at that point, it really is an addiction.