The prime of an NBA player is considered to be 27-32. Pierce, Allen, and Garnet were 30, 32, and 31.
Charles was 29 when he forced his way out of Philly and went to PHX, and he won the MVP that year. Tom Chambers made all-star teams as well. If you think being traded, rather than arriving as a FA means a super-team wasn't "assembled" by the star player, and HOF matters but all-stars don't, then that undermines the LeBron criticism. At best you can complain about Miami, where he chose to go to Wade's team. But Cleveland had a young Kyrie who hadn't done shit, then traded for a stat-padding Kevin Love. LeBron then joined the Lakers, who had zero established talent. The team later traded for AD.