I like having both unlockable extra fighters (a reward for your dedication to the game) AND having post-launch roster expansions.
For me the problem with the latter comes with highly aggressive monetization practices. Give me a fighters pack with multiple new fighters and alternate costumes at a reasonable price and that feels like adding value to the product (example: SSBU). Price me out at expensive single fighters and single costumes and you can go fuck right off. Battle Passes and FOMO can likewise fuck right off. Anything that requires me to work to unlock something I paid for (in this genre) should be included in the base game as a reward.