Clients can only do so much sadly. For example, they can't make polls, user flairs, implement passkeys, following threads, disabling, proper blocking implementations, and etc.
Even then, the features that clients can somewhat implement (like post tags) rely on others using the same client, and aren't considered as a standard.
For the karma features, we'll be sure to disable it if we made our own instance. And as we said; the lemmy instance will always be active and the main instance.