Not true. Lewis believed in core Catholics beliefs. GK Chesterton too was a late convert. He once said he was like the church bell tower that while it was outside it was one he sounded so that folks would enter the Church. Protestantism does not have a singular belief.
“Protestantism does not have a singular belief.”
Doctrinally? Of course it does.
Individually? Common to every worshipper? No. Neither does the Catholic denomination.