Well, I don’t quite judge it by that standard - winning is never guaranteed and even some of the best teams in history can come up short, like Holland in 1974.
My standard is playing cohesive football, creating a system that takes advantage of the abundance of attacking talent in this generation’s England squad and holding their own even against Europe’s leading teams (let’s face it, Southgate’s team were outclassed against Spain and it would have been the same against Germany). If Tuchel can do all that, he will have been more successful than any England manager I can remember.