Personally, I think the "hang #16 up" is a bit satirical... and just goes to show how his personality and how he's dealt with contracts has affected his overall perception.
Objectively, he's 5th all time amongst Maple Leafs inpoints with 741 in 657 games, and even when Matthews/Nylander pass him, will be 7th.
Some of the legends he's ahead of - George Armstrong (713 in 1188, number retired), Frank Mahovlich (597 in 720, number retired), Ted Kennedy (560 in 696, number retired). By objective metrics, I think you could reasonably argue that his production is worthy of such an honour. He'd be the only non-active Leaf other than Rick Vaive to go more than a point per game in his career, and not have his number retired.
The sad part for Marner, is that in 15 years he's likely going to be invited to Auston Matthews' number retirement ceremony... and look back and realize that he'll have made somewhere in the neighborhood of $175m over his career... had he chosen to make $160m... it might be a joint ceremony with a couple of rings with a Toronto Maple Leafs logo on his fingers... and be treated "like a god" for life in his hometown.