Passive studio monitors have been in the minority for decades for a variety of reasons.
Suggest visiting the monitor review section at "Sound On Sound" site. They've reviewed a few passive studio monitors and their reviews are pretty straight to the point. Note that professional monitors, passive or active, can be expensive. One that I found was the Rogers LS5/9, that retails in the UK for $7100. (I've owned LS3/5a clones decades ago that were very enjoyable.) Another intriguing option is the Kerr Acoustic K300 that retails for $3255. Other passive alternatives are the ATC SCM 20 (not cheap), Graham Audio Chartwell LS6 & LS3/5, and the aforementioned Amphion models.
Several very good active monitors are available that cost less. The JBL 708P is one, possibly the best overall loudspeaker I've ever owned.