This is not about "writing to look smart". It's about using elegant style and using the language to it's full potential. There were multiple attempts to strip Polish people of their mother tongue and identity throughout the history, so we were taught to treasure both and use language's full richness. It's also simply nicer to listen to or read richer forms. These are the reasons for why we were told it speaks well of the speaker/writer. Also, elegance does not contradict communicating vital information. It's a false dilemma.

If it makes you look good at the expense of being easy to understand, then yes, it's a problem.

Flowery writing that you have to read ten times to appreciate is great for novels -- not so much for effective technical communication.