Let’s say that movies like Troy or 300 were box office success stories in Greece. There aren’t any movie stars of international acclaim that are Greek born so the ethnic background thing really isn’t emphasized or even discussed at all.You're free to your personal opinion but it is a bit presumptuous to speak on behalf of most Greeks. I don't buy that part of your statement. I'd be willing to bet, if polled, most would prefer Greek actors portraying Greek historical figures over broadly white actors of other ethnic backgrounds.
Back in the day Zorba the Greek was a signature film with an Irish/Mexican in the eponymous role (Anthony Quinn) and it was a non issue too. People are fully aware that without movie stars with proper accent, your blockbuster is unlikely to be successful. This has been going for many decades, in fact throughout the post WW2 period and is the norm. Nobody thinks much of it.
What does matter is when a supposedly historic show will “race swap”, like Cleopatra on Netflix (portrayed as black) recently, which irritated Greeks (but infuriated Egyptians as well). This is juxtaposed to the critique towards the (generally better received by Greeks) Netflix show about Alexander. Greek media was mostly discussing historic inaccuracies and the topic of homosexuality. Nobody cared about the absence of Greeks in the leading roles. It is a given, always has.