I don't think it's disputed that many technologies are a lot more efficient than they once were. Manufacturers of many types of machinery are driven much more by a need to improve efficiency than a need to increase power, speed etc. Materials technology has been steadily advancing and tools such as FEA and CFD have allowed designers to optimise their designs and slim factors of safety etc to a degree that would have seemed fantastical when I left school in 1989 (not that long ago). A typical large diesel engine platform will be about half the weight of an equivalent design from the 80's, with a design thermal efficiency over 50%. and much less need for intrusive maintenance. Although the expected life cycle of a platform has also halved. On the other hand regulations have also led to a lot of gaming of the regulations and in many cases actual in-service performance is nothing like what you might expect and in some cases performance may even be worse than older designs. There is a ship efficiency improvement mechanism called the Energy Efficiency Design Index (EEDI) (a mandatory one), in theory it should make ships more efficient but there is significant evidence that new designs are being over optimised for the EEDI condition and actually less efficient off that point. Something regulators struggle to understand, most of whom cannot understand the EEDI calculation and have never done anything as vulgar as try and do any of the calculations (which are actually very simple). And that is without getting onto engine emissions, cycle busting, illegal defeat devices etc.
I try to buy more efficient goods because it reduces running costs, I also think that in terms of reducing environmental impact it is sensible to make good use of goods and not just throw stuff away because it goes out of fashion. Like I say I buy my clothes at a shop we have here called M&S because their men's wear is good quality, durable and by dint of being rather dull and sober tends not to go out of fashion by dint of never having been especially fashionable to start with. I commute by train and prefer to avoid flying (but in fairness that's because flying sucks more than any environmental concerns). I do it because I think it's a right thing to do, and it is also thrifty and I see no reason to spend needlessly. My objections to a lot of eco-sustainability type arguments are not because I object to what is being promoted but rather to the concept of government compulsion and abrogating personal rights and responsibilities to governments. I object to that on principle and I also don't like the dismissal of individuals as being incapable of doing things for the right reasons (and if they don't then that's there choice). And I do find it hard not to be cynical about both the motives and competence of many government regulators.