Well they aren't unraidable, they are just harder to some extinct than your average block on the ground.
Just need to use creativity to bypass the normal means such as ramps, stairs and blocks to acces the building. There's a reason why there are gigantic twig skybridges beside these rock and lakehouses.
People go up and build skybridge above the building where the cupboard restriction has no effect and then jump to the roof with C4 and blow the roof and enter that way or jump to the front door if it has even a slight ledge from the rock and it wasn't build on the very edge and then just blow the door and walk in. And since fall damage doesn't really kill you until extremely long falls, this is totally doable if you have 1-2 food with you.
There's usually always a way, some just take a little more effort and planning. Not to forget scouting, it's not unusual to sit for hours on camping house observing residents to come and go and making notes how they behave, which doors they use etc. In legacy i spent probably around 4-5 hours just camping one guild house and waiting to see when they all went to bed and then raided them, they went in and out with full kevlars and guns and raided and killed a bunch of people, while i sat naked hidden on a rock near their house and timed their routes and observed which doors they used to enter the building.
Without server wipes there's literally infinite resources to be used on either building or raiding, then only time available is the only restriction.
Twig costs 50 wood a part so with 8-10k wood which is one hatchet worth of wood you gain access to these houses easily.
your quit right we have all done it
but this is far far harder than just walking up to the front door, because now we can ...at the very best the house owner could destroy the access bridge with a hatchet every time he enters is house but thats not going to be always possible or enough and its a pain in the ass to do
and with the current state of doors every house is an easy target and thats not fun for anyone