I think that’s a fine mentality for redraft leagues, but in a keeper scenario I’m not sure it’s as practical. For example, I took over a team a week or two before the 1/31 cut-down deadline. I don’t have a shot at winning the league, but I do have a shot at 2nd/3rd, so it gives me something to manage toward while I’m retooling the roster to try to make a real run next year. Also, there are just too many leagues where only a few teams have any realistic shot of winning even before the season starts.
As for the deadlines, I agree, the cutdown deadline shouldn’t be the same day as the renewal deadline.