My heart goes out to everyone on this thread.I have been exactly where you are - multiple times.Being overwhelmed by being downhill of Sales, and rightfully so.My recommendation is to start:1. tracking retention and churn like a hawk2. are the churn % increasing as the deals get muddier and the company further drifts from its ICP3. tracking the reasons WHY customers are leaving (unfulfilled promises, unmet expectations, etc.)4. how much $ is lost5. does your company track at all how much it costs to acquire new customers?
It is always tough to convince the company to not focus on bending over backward for new prospects because they only see the new revenue.
Now with that said, there should be an ICP for your company. If the feature that the existing customer is asking for is something that fits into your ICP, then it really should be something that new prospects will want to see and use as well. The main method to solidify this is to query your other customers to see if that specific feature is something they would utilize as well. If you go to your product team/person and say this one customer wants feature X is different than if you say, this one customer is requesting feature X, and these 10 other customers that we have also would like that feature.
Now if it is only that one customer that wants that unique feature, well that is a completely different topic in the realm of CS. That means this single customer wants your product to bend to their unique business practices, which happens a lot. If this is the case, we will have discussions with that single customer about that unique feature and how much it is going to cost them to implement it just for them. That candid conversation usually ends in them forgetting about the feature because it was not important enough to spend more money on it or they end up discussing paying for the extra development.