its not a problem, its a theme.
even arcs themselves mirror each others. that doesn't happen out of laziness. thats planned.
Of course it's planned ... just nor a creative or good plan at all.
Literally every arc is structured the exact same way:
1. Arrive at new island, get split up, meet locals.
2. Learn about some serious problems in the country.
3. Meet the villains for the first time.
4. Have a clear setback and "lose" (in whatever way) to the villains in the first round.
5. Flashback of the countries' hero/heroine and how the villains turned everything bad.
6. Some huge threat for the whole country is revealed (nuke in Alabasta, advent of thunder in Skypiea, Buster Call in Enies Lobby, Shinokuni in PH, Birdcage in Dressrosa etc.)
7. Gathering up together and getting ready for the final round against the villains.
8. Winning their battles and saving the country from the huge threat.
9. Party/Banquet
10. Sailing on to the next island.
Oda has used that same old blueprint almost every single arc for 25+ years now (only slight exception being the stretch from Amazon Lily to Marineford).
Of course people get tired after reading 1050+ chapters of the same old stuff in different clothing again and again.