The general consensus in Christianity is once you become a Christian you enter into the new covenant ( the body of Christ ) and that is your salvation. As long you believe in the basics it is pretty much all the same ( Jesus was god in the flesh, you are saved though grace etc etc ). Most of the differences in Dogma are really quite minor and unimportant. The pastor at my church (evangelical ) says you could go to Catholic church tomorrow and as long as you were sincere , it wouldn’t matter.
Now why don’t other churches have an axe to grind the JWs ? Well, JW are considered well-meaning but dangerous weirdos. We are educated about them but there are literally thousands of cults and every Sunday can’t be cult awareness week.
Also devoting every other Sunday to the Book of revelations and Daniel is stupid. Trying to crack codes and discover the identity of the whore of Babylon is stupid.