One very large component of user happiness is the intuitiveness and familiarity of the user interface, and following user interface guidelines of the host opera

One very large component of user happiness is the intuitiveness and familiarity of the user interface, and following user interface guidelines of the host operating system (i.e. the patterns and conventions that the user has already been trained on) will help tremendously with that. That doesn't mean that you should never stray from those guidelines in a pursuit of a better UI, but all other things being equal, diversions from the standards should have to justify themselves. Things like using an Android-standard icon where there's an equivalent in IOS don't come anywhere close to that bar, in my opinion.