Yes, for 8 years now, Apple has not allowed users to add things to iOS other than what you find in the app store -- not fonts or keyboards or apps from elsewhere, etc.
The place to make your points where Apple will see it is
The iBooks Author app has the ability to embed fonts, if that app could be used for your purpose
Thanks for Author.app tip. I've only played around with it a bit so I have a closer look. I want to be able to distribute the Keynote to a community of users who can make there own edits so it wont really work for me in that contetx but maybe in others.
I've been giving Apple feedback for years, both on that link and direct emails to members of certain development teams. I'm unconvivnced Apple heirachy listens to any of it. The only thing remotely like listening was a suggestion I made for a thing kind of like what was to become Magic Move transitions in Keynote. I was asking for a 'duplicate slide with all objects in *end positions after builds*' to facilitate complex transitions and build sequences.
I'd still like that duplicate slide with objects in end positions command Magic Move is more of a Ken Burns effect (to use Apple's iMovie nomenclature). If you want to use custom builds to do you animation and need to go to a new slide because it's all getting too much complexity for one slide (animation move paths are terrible to use as is lack of North and West pasteboards) you have to recreate all the end positions and line up with guides, it's hideously time consuming.
I've probalby got a list of 30 or so suggestions for Keynote apnd seeing as Apple has advertised positions on iWork dev team ove rhe past two years maybe there's some hope of improvements one day. Maybe released with a redesigned Mac Pro wouldn't that be nice…
No user fonts on iOS for 8 years is enought to make me investigate Andriod and to be honest I real DON'T want to go there.