While it's true that different religions may contain
some truth... if they are teaching something false about what is most important (i.e God), then it's a false religion.
Most of the world religions contradict each other when it comes to what is most important. Therefore, logically they cannot all be true... or even "one part of a whole," as you put it, if they are teaching contradictory things.
Jesus made it perfectly clear when He said, “I am the way and the truth and the life. No one comes to the Father except through me." He didn't say anything about blind people touching parts of an elephant, or different religions being "one part of a whole." He didn't say there were many "paths" or many "doors." In fact, He said the opposite (John 10)
The nature of truth is narrow, exclusive. 2+2=4, not 5 or 6 or 7. So what Jesus said in John 14:6 goes along with the nature of truth itself.
It seems that some people come up with a god in their mind in the way THEY want God to be. I think that's where the "all paths lead to God" mindset comes from. But that's going about it the completely wrong way. It should go without saying that truth isn't dependent on us, on what we want or what we believe. It just is what it is. That's why it's so important to seek and find it.
The bible says Jesus is the Word of God, and the Word became flesh (
John 1:14). If you want to know God, look to Jesus.