Couldn't agree more! Have been wrestling with a near-unusable iTunes since update to 12.3.1 and have been extremely gun-shy about trying other solutions mentioned. Now, PROBLEM SOLVED! Turned off "automatically check for updates" in iTunes preferences, but have not yet been able to "hide" the iTunes 12.3.1 suggested update in App Store. Right-clicking on it as noted elsewhere only brings up dialogue box allowing me to "Skip This Update" manually. Oh, well - good enough for ME.
To be clear, I'm talking about the method of un-installing iTunes 12.3.1 suggested by Plux Quba on previous page of comments. Was able to delete iTunes from system, download iTunes 12.3 elsewhere and install. Opening the new (old) version of iTunes immediately recognized my library and began to play without issues. Cannot express how relieved I am!