When I learned Hungarian in Hungary my fabulous teacher always translated the you plural pronouns as 'you guys' so as not to confuse it with the you singulars. Why doesn't DuoLingo do this? It would be much clearer in English!
I think it's enough that it says you (plural) and you (singular). "You guys" also isn't really a pronoun. "Y'all" would be more appropriate, but it's nonstandard. Besides, a lot of users aren't native English speakers and can easily realise the difference between the two - English is a fringe case.
But the issue is that it does not say you (plural). When I included that in my translation from Hung to Eng I was marked wrong. So there's no way to indicate in the translations into Eng that we are talking about multiple people unless you say 'you guys,' 'you all' or the unforgiveable 'y'all.' So DuoLingo can't really check that people know the difference between singulars and plurals...
I think one problem is that there is no universally-accepted second-person plural form in English -- in some places, they use "you guys" while to others, that sounds wrong, and they might say "you all" or "all y'all" or "youse" or .... instead.
So whichever one Duolingo might pick, it would look wrong to others.
Irish for English is a little different -- I believe they standardised on ye which is apparently common among English speakers in Ireland.
But there aren't many native English speakers in Hungary so you can't go by what they would use; instead, you have to basically cater to a world-wide audience, and then there's no one form which wins.