You don’t have to use a broker but you might find:
1. When getting a direct quote from the same insurance company, the premium stays the same or is very close.
2. Dealing directly with an insurance company when making a claim is going to require a lot more time for a committee member.
3. Getting annual comparative quotes will have to be done by someone else who is competent to do it.
AFAIK both insurance companies and strata managers see the brokers as assisting in their offerings and might adjust their fees accordingly if they are not used.
Let us know!