well, cleaning to prevent pests is a luxury, because it implies you have something to protect in the first place, and that makes you a wealthy man in urw.
when surviving in the wild, moving with my dogs and kota, i find the game to be very realistic, fishing to is very well done, hunting is amazing!
but once my homestead is done, i find myself idle 75% of the time, when irl to run a homestead like that with those tools i'd be working all of spring, and half of summer. prepairing land takes a lot of effort, even if you use the slash and burn techinque, the weeding is much more time consuming then the planting. and if you leave edible stuff everywhere (like a cellar) that's bound to attract pests, it also gives another difficulty at the later game stage without having an effect on the early stage.
as for hygiene, that to would be nice to have a use for, preventing disease is one thing.
needing to feed your animals gives a great chore, the chicken co-op mod already does this, if i want eggs, i'd better get some form of chickenfood first.
and of course, being so busy, heatstroke is a real danger, a simple footbath can do wonders against that
these small adjustments could make the farming lifesteal much more realistic, and combined with the planned building decay would keep you busy, preventing a single man from being richer (and more bored) then an entire village.
when you have all the tools, and you have all the foods, and you have 3 full sets of metal armour, and a pallisade wall around your homestead you'd find yourself to be a very busy man maintaining all of that. but in urw, you can just keep stockpiling stuff.
about slash-and-burn's purpuse, it's mostly as fertilizer. it also removes weeds making prepairing faster and less tireing, but not really that effective against the weed's roots. it still takes a lot of manual effort to remove those.
you use fire and ashes to prevent soil degredation, together with migrating your fields (crop rotation in later forms, ancient fins just moved a bit).
neither of those prevent weeds from growing back tough, and the better the soil the worse this gets. if you leave your crops alone for 2-3 weeks there won't be that much left for your crops to grow or make the parts that you'd like to eat, depending on what type of crops you are growing and what stage of growth they are in.
you also have crop diseases and pests or even storms that can ruin or seriously reduce your harvest, some of wich you can take action against. a fungus or slow-spreading disease can be removed, bug infestations are very hard to deal with without pesticides, chickens do have a use against bugs but they themself can be bad for certain crops that they reconize as food, or for young/small plants.
wildlife can also treathen your crops, but the game already simulates this for the animals it already has. birds steal seeds and berries, rabbits eat the green parts of your plants, rats can even dig out potatoes, i have no idea what the fins used to do against those animals, irl i use cats.