So, who needs Super-Massive Black Holes when you have Dark Matter, or Vis-a-Versa?

At first we didn't know about Black holes

We still don't know what Dark Matter really is

'Black Holes' in space are the same as 'Whirlpools' that are caused by flowing water.

What is flowing to cause Black Holes is matter. This matter moves at different velocities , just like flowing water over a rocky constricted bed.

As to the universe, what we need or what we don't need was never or ever will be our choice - learn to live with it.

Galaxies don't have 'seams.Sarcasm doesn't work and has no place in the scientific method except as form of distraction. There is plenty of evidence that indicates almost all LARGE massive galaxies have super massive black hole, Sometimes there are TWO super massive black holes in for galaxies that are going through each other, which what will happen with the Milky way and Andromeda 1 (M31) galaxies. BECAUSE of gravity.

If you are claiming that that the data has been misinterpreted, please provide BOTH your data and alternative explanation and evidence for why super-massive black holes do NOT exist and are not needed.

After a study of several supermassive black holes - they’re about 1/1000th the mass of the rest of the galaxy; which isn’t really enough to hold the galaxy together (by comparison, the sun is about 99% the mass of our solar system). So, mainly it’s thought that the mass of stars and Dark Matter may be what binds the galaxy together (Did you read that in Obi-wan Kenobi’s voice?)

substituting fictional dark matter and dark energy for incorrect calculations is not true science , when observations and calculations don't match you look for the reason not invent a fantasy factor to compensate

If you didn’t need both, you wouldn’t have both