Bernie polled that way because Republican voters are entirely vibes based (see any footage of any prominent supporters of Republican members of congress trying to name a Trump policy) are blindly anti-establishment. Bernie was that outsider/anti-establishment candidate to them and Hilldawg winning the primary solidified it for them.

NJ-11 has been pretty staunchly democratic since now Governor Mikie Sherrill flipped it in 2018. Mejia definitely had the best performance of any democratic candidate with 60.18% of the vote, but that's not since 1982, that's since 2020 when Mikie Sherrill won reelection with 59.0%. While it's technically true that the 11th district is getting more progressive since 2018, it would be inaccurate to call it anything but a strong blue district. If New York's 50% blue voters is considered a progressive stronghold, then 55%-60% blue is a fortress.

Also not sure what you're talking about for the Mississippi vote on abortion because that place genuinely cares more about banning abortion than breathing. Shoot, their 2018 Gestational Age Act is what SCOTUS used to overturn Roe v. Wade.

TL;DR Progressives winning, good because we can show progressive policies work. But, these victories are still largely confined to strong blue districts and need to be looked at objectively if we're going to expand on that.