You can buy each of the five "challenger packs" included in the first fighters pass seperately. I imagine the second fighters pass will also offer it's six pieces of content as individual purchases too.
Good to know.
Except they did do pointless DLC for NSMB2 and FE: Awakening on the 3DS. I also didn't like that the base game for Mario Golf had very few courses because they held them back for DLC. The base Mario Golf on 3DS was a joke. So there are some examples of bad DLC handling in the past.
I am aware of all those things, but they have no relevance today because Nintendo has moved away from such DLC approaches. The Fire Emblem series was the worst offender with three 3DS games where only the additional campaigns for Fates were priced appropriately, but Three Houses on Switch uses the expansion pass model. The final verdict for the Three Houses DLC is still pending because its meaty part (an additional self-contained sidestory) releases in mid-February; the extras for the main game (new quests, monastery activities, optional battle maps and costumes) that have all been released in 2019 aren't more than a side dish in the expansion pass package.