By that, he talks about its low demand, low resale and that they are not very common here. They have no quality issues, so no worries.
In well known brands, made in China does not matter at all. Next time you see that shopkeeper, tell him to show you a used iPhone and make him read label where it says, "Made in China!".
Outer design
In outer design, Microsoft Lumia phones remind me of Nokia 3310, they are almost as solidly built as Nokia 3310 (brick) and one of the best thing about their rigid back cover is, it sufficiently protects their sides too.
In outer design, Samsung is usually the worst as their silver size bezels may fade with time in long term use (ruining its market value, even if the phone is scratchless itself) and back cover is usually paper thin and weak enough to break even with repeated cover opening. Even their latest premium glass and metal design is very delicate.
Inner design,
In inner design, Microsoft uses high quality Qualcomm Snapdragon SOCs and components, so no quality issues there. MediaTek SOCs used in competitors are also very good quality SOCs.
Expandable storage
In expandable storage, even very basic Lumia phones having Snapdragon 200 series SOC supports expandable storage upto 128 or 200 GBs, with apps directly downloadable and installable to MicroSD card, whereas in most MediaTek SOCs in same price range, expandable storage is limited upto 32GBs mostly. Most MediaTek devices allows direct download and installation of apps to MicroSD card too. But Lumia has advantage in more expandable storage.
App gap
There is still some app gap, but it will be filled in Windows 10 mobile to a great extent, but its a subjective matter, so one should skim through windows phone app store to check the app gap "in advance". One may not find some of his most favourite apps, but there are suitable alternatives available mostly. Many popular apps are available too, but many of them still are not. So its worth researching in advance.
Windows phone app store link.
https://www.microsoft.com/en-us/store/apps/windows-phone
User Interface
UI of windows 8.1 may not be very user friendly, but windows 10 mobile UI is great!.
Microsoft Optimisations
Since they are manufactured (hardware & software) by Microsoft and they run on Microsoft Windows mobile which is very light, so their devices are very carefully and brilliantly optimised to run perfectly on their specific hardware. This is why almost all their models run almost equally blazing fast and slow performance is never the issue!
Fast Track Long term support
Microsoft Lumia phones are alternative to Google Nexus phones. So they get fast track long term support for atleast ~2 years.
