Many people who call themselves Jews have told me that different Jewish groups are not different denominations but instead different Jewish groups are differect sects

So I looked up the definitions according to search results

https://duckduckgo.com/?q=difference+between+sect+and+denomination&ia=web

Jewish groups are newer and considered heretical conpared to one another and often have radical teachings

Where as Christian groups have been long established and are considered legitimate

Not according to my words but by reading the definition