I'm going to roll my eyes: if you read the change it's literally 'Instead of cmd-clicking, you need to hit 'okay cool' in the control panel', not YOU CANT RUN UNSIGNED SOFTWAER!!@11!!111
The reason for this change was, shockingly, because malicious asshats were putting up malware pages telling people 'oh you have to cmd-click to install totally legit thing here!' and this puts a nice warning up in front of less-educated people in the hopes of preventing the spread of malware.
I'm 100% for this change since it literally adds 3 seconds of clicking a single time for an app, and makes it where my family members are less likely to get totally screwed over.