Variable Displacement Compressors have been around for at least 30 years, Though they had a clutch & the Control Valve is mechanical. The Harrison V5 was the first one I ever ran across.
The new variable displacement compressors use a solenoid (PWM) to control the control valve. These come with & without clutches.
It's a little to soon to call electronic controlled V/D compressors unreliable, GM trucks started using them in 2014 albeit with a clutch & seem to be reliable......A lot of them are replaced for a leaking discharge line.
The earlier V5 & V7 Harrison were known to leak at the body O-rings.....Nothing to do with them being variable displacement. The Harrison HT6 fixed displacement compressor had the same affliction.
Some vehicles (Especially Japanese econoboxes) have poor A/C performance in really hot weather, My wifes 2010 Toyota Corolla & my daughters 2009 Honda Civic are prime example of that. Sure...They will eventually cool the cabin down, But takes what seems like forever on a 107 degree day.
Small evaporator cores, Small condenser cores, & small refrigerant charges add up to poor performance.
My 2500 pick-up & Camaro have huge evaporator cores & blow cold air within seconds of start-up, Both use fixed orifice tubes though I don't think that is a huge factor as I've had THX systems that perform very well in the past. The truck is fixed displacement & the Camaro is mechanical variable displacement.