Okami13_: Reddit user claims that they've figured out what causes Monster Hunter Wilds performance issues – and it's kind of wild.

According to their investigation:

• Owning more DLC = more FPS
• This is due to an aggressive check the game does to see what DLC you own
• It is NOT intentional by Capcom but this constant check causes performance dips
• The user created a mod that tricks the game into thinking you own all DLC and noticed immediate improvements
• All information has been sent to Capcom support
• This same user has already already helped Capcom solve a performance issue in Dragon's Dogma 2

(via de_Tylmarande / Reddit)