I don’t think it’s about being too old to enjoy the car. It’s about possibly being old enough to afford the 5 series equivalent, which is an up-sell. He’s just a slimey salesman doing slimey salesman things.

Wouldn’t worry about it. Try both, he could be right, or he could be wrong.

Turbos, direct injection, variable valve timing/lift, materials, engine management systems (ecu software), compression ratios, cooling.

Turbos and direct injection are probably the primary drivers in power, but improvement over time comes from many small improvements in all areas.

As others have noted, modern cars are massively more _efficient_ than older cars. That doesn’t necessarily mean they consume less fuel - it means fuel/power conversion is improved, so your engine does more work for the same capacity.