They had the scriptures back in the 1st century and still rejected him:
John 5:45 Do not think that I will accuse you to the Father: there is one that accuseth you, even Moses, in whom ye trust.
John 5:46 For had ye believed Moses, ye would have believed me: for he wrote of me.
John 5:47 But if ye believe not his writings, how shall ye believe my words?
So what you are implying is once they see him whizzing out of the clouds someday they will suddenly wake up.
So now it's salvation by seeing and not faith then?
Well other than the 2 witnesses at Jerusalem, there are to be 144,000 witnesses converted of the Jews at or after the great tribulation. Seems like God the Father has chosen whom would believe in Him "afterwards" to serve as His witnesses.
Don't forget, during the millennium reign of Christ, new generations yet to be born are going to be able to see Him and after a thousand years, choose to either side with the devil or remain loyal to Him; hence not exactly saved by faith, when He is in their sights, but yet by applying faith in Him is how they are saved.
I believe that s why Jesus sad blessed are they that have not seen Him and yet believe for the time we are in is the only time saved believers can run that race by faith in Jesus Christ to be received by Him as a vessel unto honor in His House at the pre trib rapture event.
Those left behind and new believers can only be received as vessels unto dishonor in His House.