He wasn't the system, Phil was the system and he was successful with and without MJ. You can look up those facts just google 1994 Bulls, 2000 Lakers, 2001 Lakers, 2002 Lakers, 2003 Lakers, 2004 Lakers, 2008 Lakers, 2009 Lakers, 2010 Lakers, 2011 Lakers.
Also google 2002 and 2003 Wizards if you want to see what MJ was like without Phil.
In addition, Lebron has been dominating the NBA since Rudy Gay was at UConn. Lebron never retired, Lebron never had a down season, every team Lebron plays on gets instantly better, every team Lebron leaves gets instantly worse, and he's still in his prime in year 17. MJ was was retired for the third time after his 15th season and again MJs last two seasons were pathetic.
The GOAT doesn't have or need excuses.