Garling isn't on the level of Garp, or Roger or any of the top tiers involved in God Valley never has been and never will be
Other than Garp the average VA is Franky tier at best
The "Garling is not a top tier" reminds me of "Gorosei are not fighters" once again
Oda shows this man 3 or more arcs prior Mary Joa arc for one reason, not only that... he stated his position as the Supreme Commander... not only that... he made sure to state that this man was in God Valley with other top tiers and not only that, he's old, meaning he got experience (and we know how Oda and Japan likes their old man).
And he was introduced as the leader of a group, and we didn't saw the rest of that group meaning he's league above them.
I may be coping, but imagine seeing a Page One back in Dressrosa like why I'm seeing a fodder 3 arcs prior Wano Oda?
But we saw Kaido!!! Because he had importance on the plot, the same goes to Shanks' dad.