This doesn’t answer the question about needing more than 50.

Even if there are 20 departments, a development, testing/qa, and production server environment, phones, printers, 12 conference rooms, a dmz, an IoT, staff, and guest wifi, backups on their own vlan, a management vlan, and multiple vpns, you would still come under 50 with a few more to spare.

If you have a network like this it might also behoove you to physically separate it out so guest infrastructure and production, and management interfaces are all on completely different devices and thus each network doesn’t need all vlans.

Unifi doesn’t sell the highest quality of equipment that could necessarily support more complex environments in the first place but needing more than 50 vlans on one physical network sounds almost unsustainable.