And this is what I worry too. Not just in developing markets, but everywhere. I buy a very large amount of used tools and electronics, but recently new tools and electronics have gotten so cheap it usually makes much more sense to buy new.
You can get a slightly older phone used for about $200 or so, but there are plenty of great brand new options around $200 as well. You can get someone's old angle grinder used for $10, but you can buy a new one with a warranty for $14.
I personally don't care about scratches or heavy visual damage on my stuff, so buying used usually makes sense for me. But nobody wants to sell their old stuff for as cheap as Chinese new products these days. Even if they do, the Chinese stuff comes with a warranty and a promise of support and refunds.
That's what worries me: at some point, manufacturing new stuff just gets so cheap that it outweighs buying used even for the most hardcore thrift shopper like me. I recently bought a nice looking pocketknife with a pretty wood handle for $3.49; in a thrift store you'd see a used one for maybe $10. I recently got a used angle grinder for $10, but it broke, leaving me wishing I had bought a new one from a local store for $14 (including disks and a 2-year warranty!)
The worst thing is that because of lower-quality manufacturing for decades, many used things have very little inherent value. When every particleboard table cost $25, a used one was worth maybe $7. But now that you can get a new particleboard table for $5, the same used one is worthless. The same goes for a billion other things, from calculators to drills to speakers. In the past, when cheap new things weren't available, the used low- and mid- quality versions of those things held value. Now, anything that's not high quality does not hold value. When you can buy a used calculator for $3 or a brand new one with a warranty for $4, nearly everyone will pick the new one.
TLDR: When cheap Chinese products are available, used low & mid quality products become worthless and only used high quality products hold value. This will cause enormous amounts of unnecessary waste to be produced.