I don't think anyone would call it trivial; it might be that the submitter erroneously translates elementary as trivial. Here elementary means that it doesn't

I don't think anyone would call it trivial; it might be that the submitter erroneously translates elementary as trivial. Here elementary means that it doesn't use higher math (calculus, analysis, etc), it doesn't say anything about ease or complication, and indeed the elementary proof of the prime number theorem is hella complicated.