Yes, because the system is massively tilted towards the incumbents. The combination of gerrymandering and party support favors incumbents very heavily. In fact, that issue is exactly what I was talking about in the OP - the party's desire to play dirty in order to artificially inflate the prospects of incumbents even more.You listed senators and congressmen and women who have been serving for decades and comfortably winning elections.
But your party doesn't believe that. Your party doesn't believe in letting the chips fall where they may, your party believes on stacking the chips in favor of the incumbents and screwing over challengers. That's the whole point of freezing out any vendor who doesn't agree to unilaterally support only incumbents and nothing but incumbents.You and I will always fundamentally disagree because I think candidates should run on what they believe and the chips fall where they may.
My fundamental disagreement is that I believe ideology and practice should trump all. While the Democratic party believes that the power of the party and the welfare of its establishment candidates is in itself an objective good.
Imagine this scenario. Imagine someone came to the establishment Dems in a secret closed-door meeting and told them, "I can guarantee the liberals 60% of both houses and the presidency in the next election. The only cost is that every single one of you incumbents will have to give up your seats. You will lose your seats, but the country will be better. Otherwise, you'll win your seats but you'll remain in the minority."
Would they take that deal? If you have paid the slightest attention to how both parties have moved in pretty much all of recorded history, you know there ain't no fukking way they'd do it. Not a chance.