This has nothing to do with things that may or may not be "illegal".
The only circumstance is with my consent.
Unfortunately I cannot prevent physical intrusions. When it comes to security of data however thankfully things have been improving.
Whilst I think that of course people should stand up for civil liberties etc we have to bear in mind if we completely neutered the police your civil liberties aren't worth shit as a criminal can just take them from you as nobody has enough power to gather evidence against them.
You then risk people turning to mob justice with no due process whatsoever.
Police can serve warrants to search my home. There is nothing I can do to stop them, and I won't attempt to stop them (since I value my life). However that does not mean I consent or approve. "They have a warrant", provides me with zero comfort.
tl;dr: Police are going to keep being police without my approval, so I don't see why my system of ethics needs to give them room to operate.
without this, almost no crimes would have enough evidence to go to prosecution. that includes stuff that you don't care about, like privacy, and maybe stuff you do care about, like murders and kidnapping
This isn't really a problem. Cops can get a warrant to search your house, and I'm pretty sure they'll find some things that aren't illegal, but are very personal.
If you restrict evidence finding procedure to those in which only evidence (and nothing else) can be found, then I'm pretty sure you'll end up with no evidence.