You can reject the part of the religion that talks about everyone else going to hell, and just believe the peace and love stuff. It’s probably easier to do this with Christianity than with Islam; we don’t really know what Jesus’ views on religious exclusivism were, but if he was as loving and humble as the Bible makes him out to be, he was probably an inclusivist as well to some degree (meaning he probably didn’t really say a lot of what the writer of John ascribes to him). Mohammed on the other hand had a lot of people killed who didn’t agree with him; guess that doesn’t fit so well with an inclusive religion.
I agree that some world religions would never endorse an inclusive religion. In fact I would not expect my Catholic Wife or Children to accept the concept of inclusive religion, I would prefer that they stay within the comfort of their beliefs,
but I also believe that anyone who has met a Muslim, Jew, Christian, Hindu, etc etc has trouble believing that this person is condemned because they were not born into the “right” religion. For this reason we look for explanations of how all religions can be true, or at least partially true.
This approach reduces the personal experience of being a devout believer but increases the opportunity to experience many differing views.
I think the issue of specificity important too. any religion that avoided specific absolutes (like thou shalt not kill) would stand a higher chance of being obeyed and perhaps believed. Morality breaks down at absolutes.
Better to look for common ground and build on that.