A century ago the person who said "If you was..." would have been thought to be using the language correctly!
"If you was" being the subjunctive (used in a hypothetical sentence) where "If you were" is the indicative (used for making ordinary statements.)
Probably most of you, like me, still say "If I were you I would do such-an-such" again the subjunctive, as I am not you, nor am likely to become you! Where " I was going out, when the phone rang," is the indicative.
I don't really mind yous as the plural of you, because I grew up outside Glasgow where at least half the population regularly used it. I myself do not, having been taught that it was a dialect form, not to be used in correct written or spoken English.
It takes all sorts to make a world; this applies to language as to everything else.
I also distinctly remember the elder generation criticising our use of the English language when I was a child, so I think it is a perennial problem.
"Things ain't what they were! " And, "No, they never have been!"