I don't believe there are any perfect translations, and part of the reason for that is that there is no perfect manuscript in existence. So when you've stated that the Greek manuscripts found after the KJV contained errors, that point also applies to the manuscripts that the KJV translators used.If the evidence was better, I would agree with you. However, the manuscripts uncovered are inferior to the manuscripts used to translate the KJV. These newly discovered manuscripts contain errors and flat out lies. Again, older does not mean better. Older in this case, IMO, means they were discarded because they were subpar. In fact one of these new manuscripts known as Codex Sinaiticus was discovered in a trash can to be burned by the monks. Here is an excerpt from https://en.m.wikipedia.org/wiki/Codex_Sinaiticus
For instance, the KJV has some interpolations, like in 1 John 5:7, this extra part was added by the KJV translators:
7 For there are three that bear record in heaven, the Father, the Word, and the Holy Ghost: and these three are one.
And let's look at the NASB for the same passage:
7 For there are three that testify:
That's a huge difference. So which version is correct? Or did the NT writers say what the KJV says?
Answer: What's known as the Comma Johanneum (the part in green highlight) is not part of any early Greek manuscript.
Source: https://www.theopedia.com/johannine-comma"These extra words are generally absent from the Greek manuscripts. In fact, they only appear in the text of four late medieval manuscripts. They seem to have originated as a marginal note added to certain Latin manuscripts during the middle ages, which was eventually incorporated into the text of most of the later Vulgate manuscripts." ^1
"The passage is absent from every known Greek manuscript except eight, and these contain the passage in what appears to be a translation from a late recension of the Latin Vulgate. Four of the eight manuscripts contain the passage as a variant reading written in the margin as a later addition to the manuscript." (Ibid.)
Now this by itself doesn't mean that the KJV is a terrible translation, but it does show that even the KJV has at least some areas where they don't accurately tell us what the NT writers said. And again, part of the problem is that they were working with what they got, and what they had also contained errors.