"In an interview with CBS News "60 Minutes", the Russia leader repeated his view that only the Syrian people can decide if and when to replace president Bashar al-Assad."
The Syrian people, or at least a very large number of them, already reached that decision four years ago or so. Assad didn't seem all that keen on going back then... hence the War.
Since then it's got rather a lot more complicated, what with ISIS entering the fray and well over 30 separate factions with varying agendas. Assad's forces are not in control of most of the country, at least in terms of area, and that makes it hard to see how the West can back him even before they spent the last four years describing Assad as a brutal dictator who had to go.
At this point picking any particular side is probably a serious mistake. There are too many to choose from. And supposing for the sake of argument that the West did back Assad, and even managed to propel him towards victory -- against whom? I think Putin's speech implies that all who are against Assad are terrorists, which is rather simplistic -- you can't turn around and ask him to leave after that.
Some incredibly complex diplomatic wrangling might be needed, to force a rough coalition of the various factions that can just about agree that ISIS is the most important enemy. Good luck with that. Alternatively, a massive peacekeeping force to set up a buffer between Assad and the non-ISIS rebels, coupled with a huge campaign against ISIS in Syria...
Every option in Syria at this point is going to be bloody, messy and probably not even all that effective. Whatever the solution, though, it will require international cooperation on a scale pretty much never seen before. I can't say I see that happening.