While one can complete a Polymer 80 build in 30 minutes or less, It usually isn't the best finish or the most reliable. Unless of course you have plenty of experience as a machinist or gun smith. It normally take me 30 minutes from start to finish to complete one. Mine are built with First Time Quality and are finished as well as a factory Glock frame.
I am a member on the Marine Gun Builder Forum and have had to help plenty of people get their builds working. The two biggest mistakes I see new builders make is that they rush the build and don't finish the recoil spring channel correctly or they rush and get the pin holes off. The second issue I see is the use of aftermarket frame and slide parts. Most aftermarket parts kits are out of spec when compared to OEM Glock parts.
And no matter what type of firearm you build at home, whether you use an 80% receiver/frame, or build from scratch, you MUST have a working knowledge of how the gun you are building works to be successful.
And to stay on topic, I haven't stopped, slowed down, or increased the amount of 80% or other home built firearms since the rule change was proposed. The proposed rule changes will end up in court and there has also been quite a few in Congress that has told the ATF to back off since only Congress has the authority to pass laws.