Unfortunately for you, the dems are the party of special elections and off year, off beat elections, and the republicans do actually show up for general elections. In midterms a higher volume, generally more educated (but somewhat more moderate/pro choice) GOP electorate turns out, and in president elections it's the magacore base, oddly the more educated Republican voters tend to vote slightly more in the midterms than in presidential years but it's not by a lot, but it was enough to flip a few seats in CA and NY red in 2022 that flipped back blue in 2024. The magacore vote is comprised of a lot of evangelicals who don't give a damn about anything down-ballot. But the black democrat vote is often the exact inverse and also low turnout in midterms.
The democrats do well when they can zone in on a single election that they can put all their eggs in that the average conservative voter doesn't see as priority and maybe the national GOP party takes for granted, like the Alabama special election for Senate in 2017, no way in that should have ever gone blue but it did, which shows the Trump era GOP are actually slightly improving in special elections for what it's worth, though the democrats are still clearly the superior party there
The seat went to the in bent by 21%, and you would expect the dems to overperform in a special election with an open seat with a GOP president, that's always how it's worked. The final margin was R+9 which, sure on the surface looks bad for Republicans, but when you take into account that the special election electorate is never as blue anywhere as any general election midterm or presidential, maybe you can average it out and say Dems overperform by half of that, so about 5% compared to what they did in 2024, which still is losing in the House given the new maps and the senate races will be individualized on a state by state case and absolutely no guarantee that the national generic popular vote will be the deciding factor of any of those outcomes, similar to the D's winning very specific Senate and Governor races in the R+4 environment of 2022.
basing projections for 2026 on blue tsunami bloodbath midterms like 2006 which was definitely pre-polarization is beyond misguided, it's fallacy.