A second language is architecture, not a toggle
Real bilingual content lives at its own addresses, which is what makes it findable and what makes it trustworthy.
A translation widget rewrites a page in the browser. Nothing new exists at a URL, so nothing new can be found in search, and the audience searching in that language never arrives.
Content prepared properly sits on its own pages with their own addresses, marked so that search engines understand which language each is in and how the versions relate.
Navigation has to work inside the language rather than dumping somebody back into English at the second click. A visitor who follows a link and lands on an English page has been told the site is not really for them.
Quality is judged quickly. Machine translation reads as machine translation to a native speaker, and in a field where people have been warned about operators, sloppiness reads as a warning sign rather than as a budget constraint.
Decide which pages exist in which languages deliberately. A smaller set of genuinely good pages beats a full mirror of mediocre ones, and it is more maintainable when policy changes.