This made me chuckle. The newer bibles are not in “better” English! They’re in more contemporary English. And in many instances are more intelligible to modern readers.
But it really depends on the translation approach taken. I prefer translations that fall within the word equivalence (formal equivalence) part of the scale. The KJV/NKJV and ASV, NASB land here. I do not like the NLT by contrast because the translators interpolate/elaborate unjustifiably imposing their bias.
Then there is the issue of Greek text the version is based on. The KJV is based on a later Byzantine text form, whereas the others are based on an earlier Alexandrian text form. There tend to be fewer scribal additions in the latter.
As for “English” the KJV was intended for public reading and this shows in the cadence and meter. It sounds great. The grammar is different, but not that difficult to master. The vocabulary is a different matter — this requires continuous study to avoid a common verbally fallacy where one reads the modern meaning of a word back into its 17th century usage, e.g. “suffer” and “prevent” which now mean “allow” and “go before”. The ASV corrects many of these, but endeavors to sound good.
I like the NRSVCE. It has clear English that I can understand.