> many people and most philosophers claim philosophy is much more than this.
Yes, philosophy is ultimately motivated by the search for truth. (Art, too, if we are talking about something like literature, is motivated by expressing the truth, otherwise it is worthless.)
> Spinoza was convinced he was "engaged in the pursuit of truth", as the article writes, and he probably thought he had built a logical proof of the existence of god [sic]. But his concepts are fuzzy, so his reasoning is unprovable, and his apparent rigorousness is not at all scientific.
Putting aside the question of whether this is true, let us assume it is. So what? This is what philosophical discourse will involve: clarifying what needs clarifying, arguing, counterarguing, etc. Second, you've fallen prey to the mystique surrounding the word "scientific" as if science were somehow more definitive or competent or whatever, or that none of these problems afflict science. And of course, that in itself is a philosophical assertion!
> Many philosophers disagree with his theories, and none of them are wrong or better or worse than Spinoza, since there is no way to refute or evaluate philosophy.
They aren't? That, again, is a philosophical assertion. And the very act of defending it would tacitly presuppose that _your_ philosophical argument is better than Spinoza's, which would make it self-refuting. Because if it's all the same, then so your argument.
> Apart from these points (proof, progress, consensus),
What is a proof? An argument. People disagree over those.
What is progress? You assume there isn't contentious.
How does consensus make something true? (It doesn't.)
> No one would claim to be an expert of a philosopher without reading and studying his book and articles. But, if the substance was more important than the form, it should not matter. One can master Gauss' mathematics or Einstein's physics without reading the original works.
This is neither here no there. The reason an expert on Spinoza should have read Spinoza is because everything that is about Spinoza's work is commentary and all commentary involves interpretation. So, yeah, if you're a scholar of Spinoza, and we have surviving works by Spinoza, it would seem rather odd if you didn't know what Spinoza said and only what others have said about Spinoza. You might disagree. The same would hold if you were a scholar of Einstein. A physicist, however, is not a scholar of Einstein, and as such, is not so interested in what he thought per se, however illuminating the original texts might be.