it's probably vapourised cooking fat that has stuck to the surfaces and hardened into a gummy varnish as it oxidises.
I find wiping over witha liquid detergent such as WUL or GP cleaner, and leaving it a while to soak in, then rubbing with a foam pad with more detergent, will get it off.
If you have a hand-painted kitchen, especially if it is not gloss, the paint will tend to be worn away.
It will be much worse on top of the cabinets, where it settles and dust sticks to it, so when you get those clean, put a throw-away protector such as paper or cling-film on the tops.
Try very hard not to let detergent or water get into the joints of the cabinets or any exposed particle board or MDF, only let it get on the painted ot laminated surfaces.
If you have a cooker hood that extracts the fumes, your kitchen will stay much cleaner. When you take out the grease filter you will see what a huge amount of fat deposits would otherwise have settled in your kitchen. You do have to get into the habit of turning it on before you use the cooker.