I get the impression you're an outsider looking in, relying on decades out of date personal experience to understand what they see.
Naturally Kotlin and Swift are in mobile games, they are part of the user space official SDK languages
Also, thumbing your nose at Indie games is odd, considering the sales they've enjoyed and the extent to which the industry has adjusted to adapt to their surge in popularity.
I can't imagine Nintendo in the 90s treating indie devs the way it treats them today.
C++ doesn't have full access to OS APIs and some integration is always required.
Adoption is driven by platform owners.