What flaws are there, exactly? Missing mutual authentication are the main cause for 2G's security issues. There are no trivial MitM attacks on 3G and 4G - besides denial of service that may result in downgrades. There are location and identity leaks, but that's user tracking at best. Not to compare with 2G.
There is no problem for a stasi wannabe to use legal process to extort the base station credentials from the phone company. There should be defences against carrier assisted MITM, like signed NONCEs and per-carrier station public key registers with accountable station data (location, station photos, etc)
If you question lawful interception, then your problem is not the technical standard that allows it, but your have a problem with society and the laws it implements.
There are good reasons to have security endpoints in the core network instead of the base stations. But it doesn't affect lawful interception at all.
What am I missing here?