If we want them to "step up" on some good things then you find ways to get SOMETHING from them.
Like it or not, much as it sucks, Manchin and Sinema hold tremendous power since it is a 50-50 Senate.
Flogging them won't help. That will only worsen things. You don't get things from people by bashing them.
You sit dwn and ask them what they WILL support and, in a situation like this, give them as much
as possible with some asks in return. What I would do is promise to move on as many of their own priorities
as possible and ask what pieces of BBB they WOULD be willing to do if we move on as many of their
things as we can. Find ways to make deals and get SOMETHING accomplished and keep trying if there are setbacks.
Impress upon them the importance of getting SOMETHING done. Say we will try to get some R support too but can't promise any. Like it or not, as of now, they have tons of power. That is just the way it is. That's how the Senate works, and it's a 50-50 Senate.

But bashing them, threatening them, insulting them, etc. sure as all hell is only going to make them dig in deeper. You never ever get what you want from someone by bashing and threatening and insulting them. You keep plugging away on negotiations.