Re-importing will show that what was exported is indeed what was expected.
I’ve noticed this multiple times that it seems like the exported file has a lower volume, but it’s not really the case. Most audio players are not set to maximum level, which is equivalent to unity in Cubase.
Your track might somewhat lower compared to other music simply because it is not as compressed. Today’s music is over-compressed. You can read all about it here Loudness war - Wikipedia