Rev 2:4,
Nevertheless I have [somewhat] against thee, because thou hast left thy first love.
Jer 2:2-5,
2 Go and cry in the ears of Jerusalem, saying, Thus saith the LORD; I remember thee, the kindness of thy youth, the love of thine espousals, when thou wentest after me in the wilderness, in a land [that was] not sown.
3 Israel [was] holiness unto the LORD, [and] the firstfruits of his increase: all that devour him shall offend; evil shall come upon them, saith the LORD.
4 Hear ye the word of the LORD, O house of Jacob, and all the families of the house of Israel:
5 Thus saith the LORD, What iniquity have your fathers found in me, that they are gone far from me, and have walked after vanity, and are become vain?
There is much in the OT about Israel abandoning God. Nothing in Paul's letters to the churches would indicate the church has, "left thy first love."
Rev 2:14,
But I have a few things against thee, because thou hast there them that hold the doctrine of Balaam, who taught Balac to cast a stumblingblock before the children of Israel, to eat things sacrificed unto idols, and to commit fornication.
Revelation says that the church of Pergamos went the way of Balaam. Balaam is found in Numbers (a book written to Israel). Israel fell for Balaam's lies, but there is nothing in Paul's letters about the church going after Balaam though.
To Thyatira John said they tolerate Jezebel and her lies. Of course we can read about Jezebel in the Hebrew scriptures (the OT), but Paul never said the church fell for her lies. He never said anything about her.
John told the church that Jesus would come upon them as a thief (Rev 3:3) whereas Paul says the church will not be surprised by a thief in the night (1 Thes 5:4).
Revelation talks about priests, kings, candlesticks, the temple, the tabernacle and other things that are uniquely identified with Israel and not with the Christian church.
There is a lot more that links Revelation especially with Israel and not the church. If you look for them, you will find them. Or just forget about and say, "that old Rich R doesn't know anything about the Bible." That be much easier! :)