It's not only Putin. Westerners like to believe some leadership change could end the war - it won't. Most the alternative parties are Russian nationalists. Ukrainian independence is only allowable in a very limited sense in their worldviews.
Would Russia be less aggressive with other non-paranoid leadership? Probably. But Russian people are like interwar Germany where they feel treated like the defeated without having been totally defeated. Seems it often leads to irrational aggression.
Of course not, refer to the "130ish people" I referenced earlier, or my comment on Russia being run by cruel people. Nationalists are all that's left in positions of power. The point is
Putin himself is wholly responsible for the conflict, the war crimes that have occurred. Crimes against humanity; genocide, the theft of children, crazy shit to inflict on 'your brothers.' So this now precludes him and his regime from taking part in any future peace negotiations with Ukraine, as per Zelenskyy on multiple occasions.
I don't know what Russia will get for a leader after Putin. Things could shift into 'high gear' for awhile and we could get surprised. More likely it's another siloviki bratva hybrid with similar imperial delusions to Putin, Medvedev or Prigozhin. Regardless, whomever takes the job, he'll sign on
without Putin's fascist war criminal baggage
or history of tossing agreements out the window when it suits him. At least initially. It won't produce trust or erase the past, but that's what Ukraine needs to even sit down at the table. What happens from there will depend on if Russians still occupy Ukrainian land and if Russia is serious about peace.
If they need to keep losing until those worldviews change, so be it. Interwar Germany was affected by the Teuton v Slav thing, whereas Russians and Ukrainians are both Slavs. I'm hoping that will expedite reconciliation at some point, maybe, but Ukrainian independence and sovereignty are nonnegotiable. I expect Russians will continue to die
en masse until this becomes clear.