What you mentioned are all established mobile games, with the ability to run multiple events sequentially and concurrently because of the IP they've built. What were those mobage like when they launched?
I would pre-emptively agree that the mobage landscape was different 2-3 years ago than it is now, and that Fire Emblem needs to do more than it is currently to compete with everything else. The problem is that you can't just run events at the pace that these established games do at this early point in FEH's lifespan.
But at launch those games all hard the same 3-4 event a month launch period and has done so since. iDOLM@STER and FGO are already past 1 year old, Granblue Fantasy is reaching the 3 year point.
So Fire Emblem Heroes definitely can. Nintendo has the money to do it. They will make that money and investment back, and more.
Granblue, within it's first month of release, had new gacha characters and story events every single week. The first big event, was a month into the game. Within the first 4 months, there were already 16 events that occurred in game with their own different objectives, on top of new story events and new gacha characters. Their first collaboration, was with iDOLM@STER and it happened within the first 6 months and was partially what got the game to grow even more popular on top of it's quick update rate.
Granblue, despite some gacha scandals and mass refunds, has always been pushing out new content on a week by week basis. They never had to do event reruns unless it was necessary and all reruns had extra bonuses attached to it for those who already played it.
This has been the standard for years now and even then some people think 3-4 events a month could go a little faster to 4-5 events.
To see that they're only doing 2 a month, is disappointing, but I won't know until I see how good the content is every two weeks.
Worth noting as well for people is that this game has almost 100 songs already with like 4 more added per month (a couple of which release alongside new story chapters which are far more in-depth than FE:H), it's stamina and premium currency based but gives energy drinks and jewels out like candy - so much that you can easily play without hitting any walls for free. They make their money off people going crazy for new cards of their favourite idols.
SS is my gold standard for gacha games, so going to FEH where they are super stingy with the (costly) orbs, where the pools are already full of garbage and where there is no free currency pool to draw from was quite disappointing.
It's not even just that, they have unique choreography and camera work for the 3D Lives for every new song with fully voiced events, and so much to do. 20+ million users, all within a year, all in Japan only.
Bandai Namco and iM@S is ridiculously huge and popular, which is partially why it's so successful as a game. But they never stopped updating it from launch and continued to provide content and bonuses for the user.
That's why I'm so apprehensive by the conservative 2 events a month standard that Nintendo is taking on this. It's not going to cut it unless the rewards and content provide is beefy enough to keep users invested within that 14-15 day period of the event. Versus doing an event every 8-10 days, where there isn't as much down time and enough content to keep users fresh and interested.
Like Nintendo got 2+ million users and 2+ million USD within launch period, use that money to push out more content in the game at a pace that smartphone players expect and use that money to rent out more advertising space to increase user base.
Nintendo will easily make all that money back from whales, high spenders, and casual players if they continue to push content at a reasonable rate. Especially if Jugdral is added to the game as an event and gacha. The right limited character card during gacha season is enough to get people to spend and make back your investment in pushing out new content and advertising. The market is competitive, but because they're Nintendo they're able to get people to get invested and spend, and they should capitalize that.
The game will live and die by it's support. Free to Play and Whales have no reason to stick around and keep buying if there isn't a reason to keep playing regularly.
2 a month is too slow and would risk people dropping the game because of that.