I include a game manual anyway, in addition to a future seamless tutorial/game. I know time is a limited resource, but in my case, game development is on a timescale of decades, not a few years.
If it's going to be in development for a few decade, or even longer, I am going to give players every possible resource on how to play my game. It will be youtube, in game tutorial, in game manual, question and answers, etc.
Otherwise, I agree with the idea on allocating resource to an interactive tutorial.
Dwarf Fortress is about ten years old. Battle for Wesnoth is in development for 9 years. BZFlag is in development since 1992. Freeciv is in development since 1996.
The only game that in that particular list that is still in major continuous development is Dwarf Fortress. Everybody else is a completed game that is still improvement.
Duke doesn't really count, since their development is not really cumulative.
Commercial development tend to develop really intensely for several months to a short few years and make all their money in a few months. The're short term motivated and they will never develop their game beyond that. Yet, they took the equivalent of several decade of development time and never seems to goes beyond 40 hours gameplay.
One of my pet peeves is returning to a game later. So many of them have "tutorials" or similar initial levels showing you how to play the game. You come back a month or two later and have forgotten the finer details and there is no quick summary to jog your memory. You often have to throw away current progress in order to start from the tutorial again, and the tutorial is tedious because you have already played it.
If it's going to be in development for a few decade, or even longer, I am going to give players every possible resource on how to play my game. It will be youtube, in game tutorial, in game manual, question and answers, etc.
Otherwise, I agree with the idea on allocating resource to an interactive tutorial.