You probably mean powerlevel10k[0], although that's mostly a replacement of powerlevel9k, which is only one of the (theming) plugins that oh-my-zsh commonly handles.

As for a replacement for oh-my-zsh itself, I had good experiences with zgen[1] but the fastest I've found is zim-fw[2] which produces acceptable start times for me[3].

[0] https://github.com/romkatv/powerlevel10k/

[1] https://github.com/tarjoilija/zgen

[2] https://github.com/zimfw/zimfw/

[3] https://i.imgur.com/mPPQuyh.png