Exactly. You can write a specialized product, such as 2300 AD or Zozer Games' wonderful
Orbital 2100, but then you have a narrower market composed mainly of people interested in your specific sub-genre. Your customers also have less 3rd party material they can use, as (for example) the vast amount of ship-books and deck-plans out there almost always assume gravitics and usually also have reaction engines. You can of course make a wonderful harder-science product as I have noted above, but you will have to consider the market implications.