Yeah. Check out a few books on plumbing.
You will find that you can't move any fluid without a separation of pressurized areas and unpressurized areas. That's a circulatory system when the fluid's purpose is to nourish cells.
You MUST:
1) have a device or mechanism for increasing pressure somewhere.
2) have a passage to conduct that pressurized fluid somewhere.
3) have a region of unpressurized fluid to act as a return path.
That IS a circulatory system, whether the 'blood' is hemoglobin, hemolymph, or sap.
The purpose of the blood is to nourish the tissues. The purpose of the circulatory system is to move the blood. You don't need one without the other. One element of the system alone would accomplish nothing.
All of this is irrelevant.
All you have to do is look at the existing organisms in nature and see that circulation systems come in a wide variety of relative simplicities and complexities including no circulatory system at all (just direct contact with the environment), hearts with no blood or blood vessels (just moving fluid in the body cavity like an aquarium pump), hearts with vessels distributing fluid away from the heart but with no dedicated return loop, circulatory vessels with no hearts (for example using ciliate action or compressing the vessels themselves), with or without ‘blood’ and so on.
So these features didn’t not have to appear all at the same time in one go.
What you are failing to consider is how circulatory needs change as organisms 1) get bigger, 2) transition to land, 3) get taller or take to the trees so that they are spending more time vertically aligned and so on.
Life didn’t start out requiring a full circulatory system of the kind humans have now, and most of life of this planet still does fine without such a thing. When you appreciate the diversity of circulatory systems in use today and the gradual change in body size and environments, the idea that we just HAD to spring fully formed from Zeus’s forehead doesn’t seem very convincing.
All of life is phenomenally complex. You can pick any aspect and declare it’s just ‘too complex’ to have evolved. Of course, you know that this is just an argument from personal incredulity. But the fact is, we can see animals with hearts but no vessels, etc etc, so it is possible for these features to develop independently, in some cases to originally solve slightly different problems or suited for different sizes, lifestyles and environments.
There. Just so you can’t pretend I can’t make an argument. An apology for your slurs would be appreciated, but is not expected.
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