Then you repeat the Sophist's answer, a philosophical school. Unfortunately for you, philosophy has much much more to say about truth than what the Sophists said. For example, they invented logic, and explained how to identify fallacies. So "just about rhetoric" has been shown to be wrong. This invalidates your argument 1.
Your question in 2 is again deeply philosophical: when is any knowledge "good enough"? Go on and treat this question seriously, then you will find out that some philosophers did the same already, and that you might learn something from them.
More complicated, and more to it, but certainly not of higher quality.
That said, I do think that more philosophical research is needed in the area. Unfortunately, most philosophers have focused on formal logic, even though informal fallacies are much more common.
2. Argument over progress in philosophy is a debate borne of logical positivism, and it valorizes the goal of accumulating one ever-larger shared pool of knowledge as the only one that matters. But why does it matter?
Throughout history philosophers have often been more interested in personal development than grand collaboration. Empiricism just happens to have this property of creating tangible objects that others may study, which makes it apparently dominant in a world dominated by "whiz-bang" science - we're always looking at the next big thing. But merely knowing physical properties of the world does nothing to inform us of how to use them in a productive manner. That's where philosophy will perpetually re-enter as a way to add holistic breadth: the principles are often old, but they need a new adaptation to the circumstances brought about by technical changes.
And that also means that philosophers tend to be unpopular. If their nature is always to question how we're doing things, the natural consequence is that they are outcast for "rocking the boat". This is why it is important to draw some distinction between philosophy, the contemporary academic job title, and philosophy when it is practiced by ordinary people every day. The former is a strange outgrowth of the post-Enlightenment enterprise, the latter is something anyone can claim. Defining oneself as "artist", "maker", "entrepreneur" - these ideas encode philosophical purpose.
- What is the nature of reality? - How does one acquire knowledge? - How can I trust what I know? - What is a good life to live? - How should I act on a daily basis? - What should I expect from others? - How the society should be structured? - What is the purpose of art?
Whenever I hear arguments about the contemporary relevance of philosophy, I ask myself "could these same arguments be applied to Alchemy and Astrology?" These were precursors to modern chemistry and astronomy, and their practitioners made many significant discoveries that we still use today. However, we have updated their methods significantly so though they are still known and read about, but not actively used.
I have not seen solid reasoning and evidence to suggest that philosophy is not in a similar situation.
It seems that you apply the 'natural sciences' pattern of knowledge generation to philosophy, and conclude that philosophy doesn't produce knowledge. But this stance needs justification. And as soon as you write down arguments that this is the right way to judge philosophy, you are actually doing philosophy yourself.
I'd like to ask you how you find out if a question is meaningful? And please don't answer "if it can be answered by science", because then you have a circular argument.
I do not have the time to address every bit of nonsense in this gish gallop so I'll stick to 2:
1. What is the measure of philosophic truth? It is implied strongly that "success" is determined by acceptance of ideas by others. Usefulness, accuracy, precision, ethics, are not important: what is important is that your ideas spread like a virus. If true, then philosophy is really, like the Sophists of old, just about rhetoric. And if manipulating people through words is your thing, then studying advertising and marketing would be a much more effective investment.
2. A key argument was "philosophy is so much better now than it used to be." I find the fact philosophy is not nearly as bad as it used to be, though arguably true, not very compelling. A better question would be "Is it good enough?" I have not yet found convincing evidence that is the case.