Nine in 10 Adults? So how many did you survey? 2000, apparently. Not a bad number, still a bit low to use a word describing >5 billion people.
Regarding "Adults": From where? How old? How rich? Does it include female Indians aged 50-80? Apparently they asked "Britons". Refreshing that it is not US biased for once, but that is something very relevant conveniently omitted from the conclusion while still being extremely vague.
But let's get back to n=2000. How did they get so many? Oh, apparently they used OnePoll[1], which is a for-profit company specializing in PR-surveys.
And, did you really ask "would you agree that X is a waste of money"? If I would propose such a loaded question in an academic study I would probably brought behind the barn by any respectable researcher. Ask for example "How much would you agree with the following statement: If a new smartphone model is released, I feel the need to buy it" you would probably get a very different result.
But let's not unfairly presume. What did they ask? Well, the primary source is nowhere to be found. Just a bunch of News and blogs citing each other. Some wrongly cite "The musicMagpie Annual Phone Depreciation Report" [0] which does not mention this, but apparently lead to this study.
Wait: musicMagpie? So, this "study" was apparently "conducted" by a used phone reseller, directly profiting from the sentiment this propaganda piece is selling?
Meaning, this is literally, completely, PR fluff.
I am trying hard to not pull the "HN is becoming Reddit" meme here, but please enlighten me how this uncritical reception of marketing dressed up as "science" (?) seen in this thread is different from the average /r/technology experience.
[0] https://www.musicmagpie.co.uk/phone-depreciation/ [1] https://www.thesun.co.uk/tech/12806082/new-smartphone-upgrad...
edit: punctuation