Doucoure is a great player, but probably worth no more than 50m in todays market.
Palace, however, know that Liverpool have the money and is quickly running out of options, and consequently wont entertain bids under 70m.
Liverpool have backed themselves into a corner by the Caicedo bid (which had they done their homework they would have known is a no go) and by leaving it this late in the window.
This leaves three options:
One, bite the bullet and pay what it takes for Doucoure, who is Premiership ready and who will probably improve us from day one.
Two, stick with Endo until next winter or summer, allowing them time to find value.
Three, bring in a "project" midfielder who can play as a 6 and as an 8, someone like Gravenberch or Manu Kone, to supplement Endo, but who will most likely not be first team ready from the off.
FWIW, I think they are going for option three, with Klopp waiting on Gravenberch, Kone being the back up option.