Lol, the Marine have only gotten stronger - it was explicitly stated. The Marines are stronger now than during Roger's era.
Pre-TS: Kizaru, Sakazuki, Aokiji (+Garp, Sengoku)
Post-TS: Kizaru, Sakazuki, Fujitora, Greenbull (+Garp, Sengoku), SSG (>Warlords)
Unlike the Yonko who - bar Blackbeard -...