You can probably try somthing like this – untested…
add_filter('comment_form_defaults', 'wpse379939_comment_form_modification');
function wpse379939_comment_form_modification($defaults){
// check if we have 2 or more comments..
if ( get_comments_number() >= 2) {
$defaults['title_reply'] = __('Add Your Voice To The Topic!');
}
return $defaults;
}