My observation was meant more as a discussion point, rather than an assertion, as I'm not an engineer. So no problem if others don't see the OP's question in the same way.
Over here in Europe, it seems like the manufacturers spent a lot of the 2000s developing ever-more impressive, 4-cylinder, 1.8L/2.0L turbodiesels. With diesel cheaper than petrol, giving you around 60mpg, a big tax premium on each gallon, a purchase tax hike on engines over 2.0L, and most fuel imported, it all made sense. Even if the initial cost was higher thanks to the greater complexity of the diesel design. Like many owners, I got used to the terrific torque of these engines and used to cruising on European autoroutes at 80MPH around 1500rpm: on one of these, just after filling-up, my Audi A3 trip computer showed I had 1,000 Kms range on one tank (621 US miles).
However, the big manufacturers were quietly pumping R&D money into high-efficiency petrol engines allied to the turbo tech they'd developed. Slowly but surely, with the turbos giving the torque we'd got used to and efficiency rising, the gap was closed. So even before the bad publicity around diesel emissions and cheating on MPG numbers, the gap was effectively closed (for the domestic buyer anyway): why pay that much more for a more complex diesel when you could get close to the same efficiency from a simpler (i.e. lower-maintenance) petrol engine? And so things have swung back.
If you're looking for a run-around now, cars like the Audi A1 (
https://www.audi.co.uk/new-models/a1...k/technik.html) have little 3/4-cyl turbo 1.L petrol engines that are pretty much all you need. That little 1L puts out 94 BHP and 175 Nm torque, 0-60 in 11 secs doing 38 US MPG.
But rather than downsizing to these smaller engines, a lot of us have set the 4-cyl + 2.0L as the 'benchmark' for what we buy. These are now that much more powerful, not just because of general efficiency improvements but also because of the turbo tech that's used to give us the torque we like. So the 2.0L Audi TFSI runs at 258 BHP and still does 35 US MPG.
So what am I saying? That many of us haven't really adjusted our buying to advances in technology: older guys like me still see the 4-cyl 2.0L engine as the reference point of choice: OK, a 1.8 if I can't afford much, but we wouldn't be seen dead in a 1.4L (even if it's as/more powerful than the 2.0L of 15 years ago). SO we shouldn't really be surprised if when we get our new 2020 2.0L car, it ends up leading us into all sort of trouble ....