A native speaker would add "kieli" to the end of the sentence if meaning the language and not the country. Finnish is a very beautiful language. - Suomi on todella kaunis kieli. Or "Suomi on todella kaunista." since the country Suomi is just one but language suomi is uncountable like water and therefore needs the adjective in a different form.
so, "kaunis" is for people, pets, lands, it's just as English "beautiful". and "komea" only for people?
"Finland is very beautiful." - that works.
However, when talking about language, you'd say "Suomi on todella (/hyvin/erittäin) kaunista." - not 'kaunis' (language being uncountable). But it still sounds a bit ambiguous, unless you say "Suomen kieli on hyvin kaunista." [The Finnish language is very beautiful.] or e.g. "Suomi on todella kaunis kieli." [Finnish is a very beautiful language.]