It’s a tough one TJ. I’ve never been able to come up with an answer either.
As a fan, you want your national XV to be representative of your country. If England, for example, fielded 15 players with no real links to the country – I wouldn’t watch.
The PI issue could be helped by World Rugby apportioning money more fairly to those unions rather than giving more to the rich as they do now. Then Tongans could afford to play for Tonga.
The 2nd string ABs & Springboks who haven’t quite made it is more of an issue. They often qualify through family history or residency but have no real connection to their new jersey.
I think there should be different rules for players from lower tier or non-rugby countries too. Visser, Pocock, Ngwenya – those guys would never have played meaningful rugby for their original countries.