You want somebody to lay it out for you? Okay, here it is:
The democrats agreed to raise the debt ceiling when Trump was president because they got him and the GOP to increase gov't spending to what was acceptable to them. And of course they did not want to appear to be the ones to share in the blame if a default happened. It's true that some within the GOP are not as fiscally responsible as they should be and that includes Trump, but they sure as hell are miles more responsible that the democrats are. Every time, when it comes to spending it is always the democrats who want to spend more, a lot more. And now when they have majorities in the House and Senate they are going ape-shit crazy with ridiculous amounts of spending and THAT is why the GOP is not supporting an increase in the debt ceiling. It's NOT just about previous spending commitments, it is also about not being a party to future spending that is totally irresponsible. If the democrats are determined to do that, they should also own it by themselves.
You asked what the GOP thinks the democrats were supposed to do. Well, I tell you: you were supposed to pass the legislation to raise the debt ceiling through reconciliation and done all the procedural work to get that done months ago when the GOP told you they would not assist. But no, the democrats wouldn't do that, they had to play politics and try to force the GOP to capitulate. They tried to make the GOP responsible for the default if one happened even though they themselves could have avoided it. If the democrats are going to unilaterally spend all that money that is primarily for their political agenda then they should also raise the debt ceiling to pay for it by themselves and take that to the electorate next year.