A group of Microsoft Products and technologies used for sharing and managing content, knowledge, and applications.
In modern team sites, there’s no options for us to adjust the size of the navigation.
That's incorrect. You can address most of Msft's poor design decisions like this one by adding an SPFX extension that allows you to inject your own stylesheet. In that stylesheet you can include css that will remove the truncation of text and either widen the left nav element or wrap long text, as needed. Not as easy as it used to be in classic, but Msft always manages to make simple things harder.