Joel is spot on here. I did a test clip from the season 5 finale some time ago, it was a huge difference to early episodes.
Even when just watching the DVDs: Somehow from season 4 onwards the blur is noticeably less present, so are luma and chroma issues.
And I understand your opinion on piracy. That’s why I decided not to talk about my work openly and only share it around here in a “limited” capacity, not on public torrenting sites.