If you adjust your way of doing business, you may be able to better control the variables. The group shop concept is an expensive way to go, because of the overhead these shops have to pay. But that is the price you pay for not having your own shop. The money you make every month has much more to do with what you do as a dealer, than what the group shop does or doesn't do for you. Not active enough Sales are a fickle thing and the antiques business is the most fickle of all.
Trends change on the wind.
Personal taste rules. You cannot judge your shop sales after a month or two, but you must make a long term analysis of your sales over at least 8 months time and adjust your buying accordingly. I feel like Miss Marple who knows the entire world because she has intimate knowledge of her little town. If you sell antiques, you will make money. If you sell mediocre mid-range collectibles, you will not.