This is my first time learning another language and I quickly noticed that there were a lot of what appeared to be silent vowels, for example the i in Shi, the u in Su.
After awhile I realized these were not silent, just not enunciated. In the same way the English is often spoken.
With English though, a very good English speaker will enunciate everything and it doesn’t sound strange in any way, it just sounds like they are more experienced with speech.
I can’t tell if it is the same with native Japanese, for example if I always enunciated the word DeSu and never dropped the u, would that just come across strange or do good speakers do this?