I sympathise with your predicament. I can assure you that it is possible to escape from it.
You are asking why philosophers cannot all agree. It is because they cannot decide any philosophical problems. If you know why they cannot decide any philosophical problems then you're in a position to overcome these problems and escape from all the arguing.
The reason is simple. All positive or extreme metaphysical theories don't work. This renders all metaphysical problems (as usually formulated) undecidable. As a consequence philosophers in Russell's 'Western' tradition have no method for making progress and must argue forever in Kant's 'arena for mock fights', frantically endorsing or attacking theories that have never worked and never will.
Once we see that there is just one problem to solve, which is the logical absurdity of all positive theories, then an easy solution becomes possible. The solution would be to abandon all the theories that don't work. Doh! This leaves one with a neutral metaphysical position. Problem solved.
The problem is only that this position is the one endorsed by the Perennial philosophy so is off-limits for most academic and determinedly scholastic philosophers. Thus they must argue aimlessly for centuries about which theory is the least wrong and wonder why they can't find one that is plausible. We do not have to do this!
This is such an easy and obvious solution for philosophy that your question should not really need to be asked. Any philosophy student will know that metaphysical problems are undecidable. Kant states it clearly. All selective conclusions about the world as a whole are undecidable and this is because all positive, partial or extreme metaphysical theories fail in logic. There need be no argument about this, it is simply what is the case.
Were they not so badly misled by their professors most students would no doubt see immediately what this result implies. It implies that the correct theory is the only one that is not extreme or partial. But this theory is rejected by Russell's tradition so here it is not taught or studied and often not even known.
Russell, the stereotypical Western thinker, very carefully dismisses mysticism as nonsense. He then has to to conclude that there is no knowledge to be acquired in metaphysics such that philosophers must argue aimlessly forever. This view is more or less ubiquitous in the philosophy department. He fails to notice that he has rejected the only theory that works because he does not know of its existence and never examines it. Fortunately, these days we have the internet so are able to study the whole of philosophy and escape the consequences of his decision not to do so.
It is very strange that scholastic philosophers pay so little attention to metaphysics. They already know the facts but pay no attention to them. Fortunately, as individuals we are able to walk away from their confusion just as long as we don't share their prejudices and ingrained thinking habits.
If you are nineteen and thoughtful you should easily be able to escape from this endless merry-go-round of opinion. It is not an opinion that all the theories endorsed and studied by the modern philosophy department are logically indefensible and this is well understood by philosophers post-Kant. If you explore why this is so then you will naturally be led away from the mock fights towards the only world-view that rejects all these failed theories. Then all the arguments in our academic philosophy become a side-show, a long list of unnecessary category-errors.
It's not possible to justify and explain all these issues in an answer on SE, (and I would expect some objections to this one), but if you want to pursue the topic and escape from the free-for-all of opinion and conjecture that you ask about then I'd be happy to assist. I would welcome a guinea-pig to my inaugural philosophical de-programming course. Philosophy becomes a lot easier when we reject all the theories that have been shown not to work rather than argue for them, but as you have noticed few philosophers are prepared to do this.
I would not criticize the other answers here since they all shed light on the issues but you should note that they are pessimistic. They offer no way forward but simply accept that philosophy is forever a matter of opinion. This view is optional. It arises from a disinclination on the part of professional philosophers to study the whole of philosophy and a preference for what is familiar and safe.
For the Perennial philosophy there is no similar sea of argument and opinion. In the mainstream it is accepted that all positive metaphysical theories are wrong and don't work. There is still plenty to argue about but the disagreements are of a different kind.
I'm aware this answer may seem a little inflammatory but making omelettes requires breaking eggs. Philosophy is all about arguing, even if it's with ourselves, in order that we can sort the wheat from ther chaff. Russell and his peers have failed to do this so we must do it for ourselves.
The very short answer to your question would be that the endless arguments are caused by the failure of all partial metaphysical theories. If you look you'll see that this is the only kind of theory allowed, studied or understood in the modern Western philosophy department.
