I believe KJV is as valid a translation as any other modern translation.
The language of the KJV may technically be modern (though there are grounds for classifying it as Late Middle English, rather than Early Modern), but the KJV itself cannot really be described as modern, any more than a vintage car can be described as modern. There may well be things done on the vintage car that are better done than on a modern car, but few people would actually choose to drive one for getting things done practically. It needs to be said very firmly that
any translation is simply not countenanced by any serious student, for study. Just try quoting a translation in support of an interpretation among theologians, and you won't be taken seriously again- ever, probably. Even serious students use translations to locate and point up references, etc.; but the KJV is very rarely used even for that. The 'standard' translation for many theological institutions is the RSV; also the ASV, with its improved word order, with some of the most recent versions now getting adopted. But those are only for new students finding their way around, not for anything meaty.
Of course there is the serious matter of personal use and use in public. It may well be that there the use of the KJV is analogous to using a vintage car. The chrome is deep and wonderful, the leatherwork looks classy, but for going shopping, well, maybe not. Those seats are hard, after all, and the suspension, well, keeps one in suspense- but then some of us are masochists, preferring to swim in molasses rather than water, and to make a 'cold shower' virtue of the KJV!
But whatever our personal preferences, we may be short-changed by the KJV, even in private devotions. The reason for this is that the KJV is four hundred years old, and much has changed since it was first published. The KJV's translators (and they did not actually translate much, but largely made an approved compilation from existing translations) did not even know that the Greek used in the NT was
koine, not classical. Many more, many earlier Greek manuscripts have been discovered, and intense scientific study has produced almost unanimous agreement as to the actual autographs of the NT (the only dissenters being supporters of the KJV, as it happens). Research into extra-Scriptural
koine has produced worthwhile improvements in our knowledge of verb usages and idiomatic expressions. The meanings of many Hebrew words and phrases have been elucidated by archaeology and comparative study.
Even sixty years ago, the KJV was the 'steam Bible', an old war-horse that had finally reached retirement, and, in the view of many scholars who had expressed their dissatisfaction, had been kept in harness far too long. Here is the Preface to the RSV, itself superannuated on the shelves of many, which, after expressing the 'incalculable debt' owed to the old version, admits that:
'... the King James Version has grave defects. By the middle of the nineteenth century, the development of Biblical studies and the discovery of many manuscripts more ancient than those upon which the King James Version was based, made it manifest that these defects are so many and so serious as to call for revision of the English translation.'
So those who use the KJV as 'God's Word' are in some cases, unwittingly no doubt, reading the fumbling words of man only. That is not to say that modern published translations are acceptable, because they are not- not so much because they have defective scholarship, but because they show modern 'adaptations' to modern fashions of men. But then the KJV and its contemporaries show influence of the religious fashions of their day, also, and one might at least eliminate the honest errors.
At any rate, KJV users might take due note that, for one thing, their chosen version has no name properly given to it; and for another, that the name popularly given to it, that pertaining to a secular and worldly monarch known for persecution of believers, may be of more significance than is generally realised.