When Russia "agrees" to a ceasefire and then immediately starts blowing civilians up again, it should be fairly evident that "diplomatic" solutions aren't exactly feasible.
Ukraine has drawn their line in the sand, which appears to be "Russia, fuck off back to Russia," and they so far seem willing to fight for that line. Telling them "no no no, you should give Russia what it wants, maybe disarm... you know, to save yourselves!" when Russia has proven they are bad actors whose word is worth dirt only means giving Russia more time to prepare to invade Ukraine again, likely with a far more aggressively destructive and well-trained force.
This period, right now, is as unprepared for conducting an invasion as Russia is going to be. They had no real time to pivot their economy away from sanctions and they seem to have hit them as quite a surprise. Their foundering economy coupled with having to utilize old, dilapidated technology with a wholly disorganized military that they have to constantly keep applying pressure with or else risk the whole invasion attempt collapsing means they have no time to address any of these issues internally.
Give Russia a time to recuperate and they'll use it only to modernize their equipment, plan better supply lines, train soldiers and, pivot their economy away from international dependencies and formalize economic allegiances so that their next invasion is that much more rapid, brutal, and deadly.
It seems fairly clear that Russia will invade again unless they physically can't, either because sanctions have rotted their country or because Ukraine has secured military allegiances with some powerful friends. Anything beyond those two things happening, even with some sort of "Russian peace agreement" not worth the paper it's written on, and we'll just be hearing about more blown up train stations, dead civilians and mass graves in five years.