By the Lakers standards? Probably closer to a failure but that’s only because the Lakers are such a successful franchise.
The Lakers have only had a few eras where they were not competing:
-The post Mikan, pre Baylor era (1954–1958)
-The post Kareem, pre Magic era (1975–1979)
-The post Magic, pre Shaq era (1992–1996)
-The post Shaq, pre Gasol era (2005–2007)
-The post Kobe injury / Jim Buss era (2014–2018)
All these eras are considered failures in Lakers history. The Lebron era is better than all these eras.
However, it is nowhere close to the success of the Mikan era (1949–1954), the Baylor/West era (1959–1974), the Showtime Lakers era (1980–1991), the Shaq/Kobe era (1996–2004) or the Kobe/Gasol era (2008–2013).
Lebron era is right in between these success and those failures. Obviously he won them a championship so it’s not a total failure. But aside from that one season, he has little else to show for it. So it’s not close to any kind of dynasty whatsover either.
By any other franchise’s standards however? A success. a championship is all that matters to most teams in the NBA but for the Lakers they want not just a championship but a dynasty and Lebron failed to deliver that.