If anyone joins an airline where English is not that countries first language (I’m thinking KLM, LH, AF, IB etc) then you would be a fool not to become fluent in that language very quickly.
To simply stick to English, with a few words of your hosts language, would be breathtakingly arrogant and entitled.
It’s simple really, if you want to work for KLM, expect to be able to speak Dutch, regardless of the non-Dutch requirements.
If you think that the Dutch are arrogant, and some are (just like Brits etc), it will be way worse on the flight deck or crew bus when they are all speaking Dutch and you can’t or won’t join in the conversation.