Eleven years and counting....
But hey, you do you! I will be long retired by the time anyone gains traction with a competing offering. See you on the beach!
If the sellers kind of have a big chunk of the market, and can choose between vendors, you're indeed in a difficult spot.
On the other hand, if the market has multiple sellers, and you offer a unique technology, I wouldn't worry too much.
There are differences with SaaS but they may not be as big as you think. For example, AWS mostly started as a go online with your credit card sale. Now? They have a big enterprise sales force and lots of partner relationships.
Strategic partnerships and white-labelling seem to be critical tools for growth in the current climate.
Affiliate sales have always seemed more dishonest to me than working with a vendor who adds value to our product for our shared customers.