Eh level 5 litterally just struck goal gold a few times. and haven't managed to do so since Yokai watch and I don't think they're half as important as your implying even in comparison to Capcom.
Cacom routinely shipped 4.1-4.2 million sellers on the 3DS that's a way bigger impact that Level 5 have had in japan nor globally on the 3DS. Considering level 5 have already burnt out that cash cow already i'm not getting even slightly sure why your placing them on that level of importance.
In the purely theoretical scenario that MHW was Switch exclusive same with all it's sequels like the previous generation even with a franchise contraction it would still outsell Level 5's output on the device. Even in the scenario that level 5 manage to produce another cash cow. If they hadn't the comparison would be even more pointless.
Well, let's look at the series' trajectory on 3DS in Japan.
Primary Games:
Monster Hunter 3 Ultimate [All Versions]: 1,929,447
Monster Hunter 4: 3,862,413
Monster Hunter 4 Ultimate [All Versions]: 2,693,561
Monster Hunter Generations: 3,120,442
Monster Hunter XX: 1,661,830
Spin-Offs:
Monster Hunter Stories [All Versions]: 330,576
Monster Hunter Diary: Poka Poka Airu Village DX: 117,232
And for the heck of it, the total of sales.
Total: 12,053,671
And then since you wanted to compare it to Level-5's full output:
Professor Layton and the Miracle Mask: 396,914
Inazuma Eleven Go: Light / Shadow: 455,172
Girls RPG: Cinderella Life: 33,989
Guild 01: 34,072
Little Battlers eXperience: Explosive Boost: 205,922
Time Travelers: 22,162
Professor Layton Vs. Phoenix Wright: Ace Attorney: 332,292
Inazuma Eleven Go: Chrono Stones - Wildfire / Thunderflash: 444,100
Fantasy Life [All Versions]: 379,211
Inazuma Eleven 1 + 2 + 3!! Endou Mamoru Densetsu: 66,369
Professor Layton and the Azran Legacy: 252,805
Yo-kai Watch: 1,294,133
Little Battlers eXperience W: Ultra Custom: 80,773
Little Battlers eXperience: Wars: 100,361
Inazuma Eleven Go Galaxy: Big Bang / Supernova: 277,207
Yo-kai Watch 2: Bony Spirits / Fleshy Souls: 3,169,858
Yo-kai Watch 2: Psychic Specters: 2,632,550
Yo-Kai Watch Busters: Red Cat Team / White Dog Squad: 2,167,915
Yo-Kai Sangokushi: 563,395
Yo-Kai Watch 3: Sushi / Tempura: 1,480,727
Yo-Kai Watch 3: Sukiyaki: 738,046
Layton's Mystery Journey: Katrielle and the Millionaire's Conspiracy: 115,88
The Snack World: TreJarers: 138,545
Total: 15,266,518
I don't know. Monster Hunter seemed to be going down pretty steadily. We can compare it to the PSP era to see that there was even more decline.
Main Titles:
Monster Hunter Freedom [All Versions]: 1,122,604
Monster Hunter Freedom 2: 1,723,187
Monster Hunter Freedom Unite [All Versions]: 4,223,523
Monster Hunter Freedom 3 [All Versions]: 4,835,761
Spin Offs:
Monster Hunter Diary: Poka Poka Airu Village [All Versions]: 593,475
Monster Hunter Diary: Poka Poka Airu Village G: 279,334
Total: 12,777,884
I think it takes a pretty optimistic view of Capcom's franchise management to assume that they would be putting out continual 4-4.2+ million sellers given literally every franchise they make is in steep decline compared to its high (or long since dead). Monster Hunter hasn't even been at that level in Japan since the PSP era.
Mind, I'm not opposed to the view that Level-5 is past their prime, but I don't think it's clear that Monster Hunter is a more dependable and rock solid line-up addition than they would be. They've managed to launch three hit franchises so far. When was the last time Capcom made a 1+ million selling in Japan new IP?