Perhaps you should ask yourself that question.
It is better to understand sometimes, than to be understood always.
Is Age of Empires 4X?Is Heroes of Might and Magic 4X?Is the Total War series 4X?Is Age of Wonders 4X?
Is Civilization 4X?
Is Galactic Civilizations 4X?
All these games share strong similarities to traditional 4X games like Master of Orion or Civilization, yet I wouldn't call any of them 4X.They are based in one "period" and while there are certain tiers of advancement they stay enclosed in that period.4X games on the other hand try to cover the development over a long period of time (in ingame terms) and bring drastic changes over the course of the virtual development.4X games cover the development and change of factions, only part of which is conflict with other factions.
I understand where you're coming from, but all you can really do to explain yourself is by telling me that it doesn't
feel the same as a traditional 4X game does.
You've gone so far as to redefine the genre to meet your own unrealistic expectations.
RTS games on the other hand focus on a mainly military competition of pretty much unchanging factions.
I've already freely admitted that Sins of a Solar Empire direly needs different victory conditions.
Yet, you're still missing the point that I was trying to make earlier.
For the sake of ending this debate, I'm going to tell you the answer, before this degenerates any further.
Diplomacy is the answer. All 4x games feature a diverse and complicated diplomacy setup, that changes on a whim, and forces you to adapt your play-style to the changing situation. Sins' diplomacy is much more predictable, and easier to control allowing a more laxed and fixed playstyle - That is the only thing that makes Sins more RTS than 4X.