There seems to be a dilema here, a catch 22!
The base game needs more refinement as per the 'simulation' side more so for the management/tools than display/rides/shops/etc, needs to have more intricate AI with regard to your actions/decisions within the game which will unfold a chain of events. There are many games like this where the graphics might not be state of the art but the QOL / game play is fantastic and intriguing.
You are stating that if we do not continue to buy the DLCs as they come out (even though we might not want certain ones) then in time the devs will/might pull the plug and maybe not do the sequel.
So caught between a rock and a hard place here, do we just blindly pump money in as consumers into DLCs and just hope for the best and indirectly allow a company to psychologically hold one to ransom or keep protesting about base game not buy DLCs and watch it fold with a good chance there might not be a sequel.
Software companies of course could hold consumers to ransom with regard to the DLC situation, and harness the optimism of the consumer, knowing deep down that maybe that certain company could never full fill the whole simulation as advertised!
It is a choice we as a consumers must do and we have the full power to do. There is an interim option to the ones I listed above and that is a failed DLC. If a DLC fails and does not sell as well at Frontier expected/counted on they can, and probably will, listen to why and make adjustments for the next DLC. If they keep failing over and over (meaning too few people are buying them) eventually that will lead to the support for the game over time will diminish (like RCTW). A few failures will probably be OK for Frontier as long as they make it up on a higher quantity of successful ones. In the end, if you believe in Frontier (your choice) you would keep supporting them. If you don't, you would not. Simple as that. Frontier is ion it to make as much money as possible (a business) so they will go where the money is (listen to the customer suggestions or cancel the game). Just like any other business.