To be fair that was a fairly long period IIRC. And they really put some work into that last migration once they announced everything else is going away. Minecraft has all these legacy systems because nobody knew it would be huge, so during the Alpha and early Beta periods it's just whatever payment system they've cobbled together this week.
I'm still not sure if the scattered piles of emails, account names, IDs, passwords, receipt codes or other detritus eventually persuaded them I'm tialaramex or whether the fact I'm just very obviously tialaramex (it's gestured at in my email address, it's my HN account handle, if I ever tweeted, which I do not, I would be @tialaramex, it's everywhere) prevailed and so that's why I got my tialaramex Minecraft persona connected to whatever nonsense Microsoft have. But either way, once we reached the "Now a human is needed" step they were as helpful as you could ask given how cheap Minecraft was back when I bought it.
I think if you lost all contact for so long you weren't aware there was a migration it's not unreasonable to think if you suddenly regain interest you should pay for Minecraft. The current Minecraft is very different from what you last saw, albeit not in its essentials.