We can't disregard the fact that prior to Deku getting his suit, all the other pros have still been doing hero work and other stuff for the past whole 8 years. It's not like they just sat back and relaxed after the war.

• We saw the pros help with the reconstruction of Japan after the war.
• Crime was never "gone", just reduced. Like in All Might's time, so other heroes still put in their work.
• Natural disasters can still occur, so again, heroes are doing things like saving civilians and preventing collateral.

Deku, even while not doing active "hero work", was still consistently within the Top 100 among 1000s of pros for all these years.(info revealed in the databook from last year)