Caveat: previously worked at Prime Video though not in this area, still at Amazon
That Qt application was only lightly modified for each platform, IIRC, and it appeared all over the place from those cheap Linux-based Blu-ray players to Smart TV clients. Anywhere that was embedded, generally Linux-based, and unlikely to get frequent updates.
As for some of the larger players like Roku or Android, those ones are more obvious where to hire. Java developers and BrightScript developers.
You can obviously abuse this by redesigning the UI every 6 weeks but let's not throw the baby out with the bath water.
It seems your argument is that it encourages developers to be sloppy, but in practice I think it just ends up as a net loss for users as the average user just isn't interested in updating software, however critical the bugs in their current version. Maybe I'm different from the average user, but for me the fact that chrome has gone through 90+ versions over 10+ years without me having to think about it is great (and, I suspect, strongly correlated to the relative lack of security issues over the years despite it having a huge surface area).
There are too many different stacks with their own languages (which means different library ecosystems), no good FFI/IPC options that work across stacks, massive test matrix for every little piece of the code etc. All of this, when the native differences that supposedly should make each platform unique are so few, and virtually all UI and application logic is identical. Our platform lords have basically not standardized a single thing.
And in addition, you have bugs in official native SDKs and then you end up writing your own text rendering engine, because some OS-level API didn't work properly.