I feel your pain!
Bought our place 23 years ago and did a massive amount of work on it - mostly ourselves. Including an extension to the kitchen and extra bedroom above.
The oldest part of the house (dining room, half the kitchen, bedroom and bathroom above) is hundreds of years old. It's single skin brick and very damp and permanently struggles with mould and mildew. The painting and decorating in those rooms (especially - but the sitting room and the new bit of kitchen too) all needs re-doing now - but I'm 20 years older with 2 kids and can't face it.
The dining room was only ever a bit of a bodge. The ceiling is covered in paper that has been painted so often it's crispy - and since a leaky shower when it all fell down, is now held up with tape. The wallpaper has mostly fallen off or shrunk due to the damp. We desperately need to rip it all off and start again - but are too scared because the plaster on the walls and ceiling is probably no good. The thought of all that mess is just too much - plus the work needed to make it all good going forwards.
The windows in the old bit are single glazed metal and don't fit. There are stone mullions downstairs so we can't replace with PVC or the glass would only be about 6 inches wide. Bespoke metal ones cost an arm and a leg. Every winter I have to wipe the condensation off them all every morning or it pools on the windowsills and damages the paintwork/varnish. They are leaded, and grow lines of black mould along every strip of lead, which can only be cleaned with a toothbrush and my fingernails, taking about an hour per window, several times a year.
The old parts (and some of the new) are always full of spiders and cobwebs. Woodlice live and die under the dining room furniture and slugs creep across the kitchen floor at night.
I could go on. People (used to) admire our lovely period cottage - but I'd happily swap for something clean and modern.......
I'm not even too fussy. Our kitchen is 20 years old and we did it ourselves. I still like the worktop and units, although a couple of doors have warped slightly. It's probably outdated but still functional, and while the floor and wall tiles probably wouldn't be my choice now, overall it's fine. But the things mentioned above are the really awful issues!
Good luck OP - I hope you get your problems fixed eventually!