Say I say “you like that, don’t you?”, or “we could go to Mauritius, couldn’t we?”, or “I already said so, didn’t I?” These are all ‘statement tags’, which fulfil an important function in conversation: to request confirmation whilst not demanding it.
In English, being proper and rule-bound, we do this grammatically, as the few examples above show. Hence our sentence tags are variant, being entirely dependent on the structure of the preceding statement.
Others manage it differently. “n’est ce pas?” “non é vero?” “¿verdad?”, “nicht war?” and so on. They’re all invariant, independent of what they’re asking us to confirm. I could compare them to a shrug, a quizzical smile, a raised eyebrow. Perhaps we British are not so good at body language either.
So welcome ‘innit’. Let’s de-yobbify it, make it respectable and draw it into the language. You can always pronounce it “isn’t it?” if it makes you feel safer.