In our times, being good at things is not enough anymore. You have to be a 'specialist' and in some cases, chief specialist, and you can only be one, if you have dedicated yourself to it 'solely'.
Jack of all trades and master of none. will only leave you among the mediocre. It is easy to be good at multiple things, but as I said, almost everyone is good at a lot things. But a Few are the real class.
As a generalist I find myself in high demand, commanding strong rates and being in the position of building a web or mobile product from start to finish as I want.
By defintion, most people are going to be average in the field. A little extra enthusiasm, ambition, discipline and hard work will push you out of the average.
Show me one "real class" professional who only performed in one field.
Then maybe jack of some trades, master of a handful or in the process of mastering a handful? If you take front and back end development as an example, you have many different ways to go about things on both sides. However, in terms of simply building software you can probably limit your focus for either side and deliver effective solutions. After all, the end user usually just cares about accomplishing what they need to, right?
There's too many other 'good enough' options out there. Time is a precious commodity and you'll never get anyone to make investment in your product if it's not so much better than anything else out there.
FYI, I didn't make that contention or set a definition (although you likely were talking with the GGP there.)
For what it is worth, I think you do need to make the product substantially better for people to check it out within a crowded market, but in a similar spirit to one of your other posts, there are multiple ways to distinguish your product (scaling, UI, feature set, etc.)
Jack of all trades and master of none. will only leave you among the mediocre. It is easy to be good at multiple things, but as I said, almost everyone is good at a lot things. But a Few are the real class.