While checking Japanese entries, I encountered a comment from a Japanese corrector who stated that the usage of “i-adjectives + desu” is highly not recommended. I don’t know if you’ve come across this correction, but I have a different opinion on the matter.
Firstly, let me provide you with some examples of “i-adjectives + desu”.
「家族と長い間会えなくて、とても寂しいです。」
「山頂からの景色は実に素晴らしいです。」
「大会に優勝できて、本当に嬉しいです。」
I’m not sure if you consider these sentences inappropriate, but for me, they seem quite common and natural.
I suppose the reason why the corrector regarded the usage of “i-adjectives + desu” as problematic is that it’s originally grammatically incorrect. To put it simply, for instance, “楽しいだ(楽しい + だ)”, as a casual expression, sounds unnatural, but “楽しいです(楽しい + です)”, as a formal expression, sounds natural. That’s why it’s understandable to describe it as “unbeautiful Japanese”. On the other hand, I think this can be somewhat pedantic. I’ve searched for how other Japanese people feel about this. You can check the link below if interested.
https://japanese.stackexchange.com/questions/1834/correctness-of-%E3%81%84-adjective-%E3%81%A7%E3%81%99
My conclusion is that you might want to avoid the usage of “i-adjectives + desu” if you’re a professional writer required to use sophisticated Japanese expressions. Otherwise, it’s just fine. I often hear Japanese people use “i-adjectives + desu” in daily life and in the media, but I’ve never considered it “unbeautiful Japanese”. A foreign friend of mine, who is learning multiple languages, once said that “languages are democratic”, which makes a lot of sense to me.
Languages evolve over time. We should be flexible in this regard.