>> However, in those steady-state theories, new matter was gradually created "out of thin air", and the Universe maintained its general aspect. In other words, it could continue indefinitely into the past and future, without major changes in its aspect.
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>>Today, the steady-state theories are no longer popular, because of the observational evidence that in the past, the Universe was indeed different from today. Quasars and active radio galaxies mainly appear at large distances, i.e., in the distant past.
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>Assuming quasars are correctly understood.

Did you do any reading on quasars? I think you should. For the purpose of this thread, it doesn't really matter whether quasars have a gigantic black hole at the center or not; the point is, most quasars appear at a great distance, and therefore, in the distant past. There are also other indications that in the distant past, the Universe was different from now.

For that matter, you should also do some reading on some other theories you are so quick to discard - the nature of quasars, black holes, stellar evolution, the speed of light, Thermodynamics and Entropy, etc.

A scientific theory should try to fit observational evidence, not just discard any observations lightly as you are doing. You are very quick to discard scientific theories based on a solid foundation, including observations of distant regions of the Universe (quasars and others), the laws of Thermodynamics, and knowledge about the nature of light. All this, without any particular reason. Of course, things might be different than they seem, but scientific theories should have some basis. It almost seems as if you are not trying to describe the Universe as it is (since this should take into account observational evidence), but as it should be, according to you.