Ex head of MI6 (Alex Younger iirc) was on Today earlier.
Said witkoff is hopelessly out of his depth as a negotiator (he doesn't take notes and doesn't even use an interpreter),. Besides, they fundamentally don't realise that for Putin, it's not about land but about sovereignty.
Putin simply doesn't believe Ukraine should be able to make it's own decisions. I've seen it earlier likened to a jealous controlling ex being able to still walk into their former partners home and stop them forming new relationships. Also that EU et Al are assigning too much rationality to Putin.