I have the Protestant “Handbook of US Denominations” a book researched written and published by Protestants. They document only the identifiable established denominations, as attempting to catalog the multiplicity of corner-church “guns for hire” is impossible. They admit to 224 established denominations, with opposing beliefs all over the map. Some deny the trinity. The variation in beliefs in staggering - not anything like what our Lord founded and prayed for.
The common non-Catholic practice of “church shopping” is 180º opposed to Christ’s desire hat we be one, or His teaching that we must first deny ourselves, then take up our crosses, then follow him. The fact that such practice is common in no way makes it valid, licit, Christ-like or biblical.