Dorico generally does a really good job at calculating comfortable spacing automatically, but there are times when either one too few or one too many systems end up on a page. In these situations, you do need to step in and make a judgement.
For instance, here you could push the 2nd system onto the next page, by inserting a frame break at the start of the 2nd system. As that would leave the 1st system not occupying much of the page, you should e.g. show some of its empty, hidden staves using manual staff visibility (making sure to reset their visibility later where needed).
To save everyone time, here’s a reply I added to someone else’s thread earlier today, with pointers to further information about spacing in Dorico that sound like they would help you too @Dgrady04 :