I would take this further to say that as an engineer, my most frequent issue with designers is lack of technical understanding in general. As you've noted, plat

I would take this further to say that as an engineer, my most frequent issue with designers is lack of technical understanding in general. As you've noted, platform norms are often overlooked, but so is what's feasible to implement on the platform in question. Generally, the further a design strays from native UI elements the more difficult it's going to be to implement in a way that covers edge cases well and is accessibility-friendly. Sure I can bodge something that looks like the mockup but it's not going to feel half as nice to use in practice because it required me to write a lot more bespoke widget code, and there are considerations that went into the stock widgets that the designer probably isn't taking into account. In these situations a little bit of leeway to bend designs to be closer to the OS baseline help quite a lot (e.g. do you really need that custom typeface which isn't built for use in UIs? Probably not), and so I greatly value designers who have the skill to build around what's already there instead of trying to replace it outright. That kind of design work isn't as sexy but it's far more practical.