How does a Ethereum node traverse Nat?

For true decentralization of an app a Point to Point internet connection without a centralized signalling server involved is a must. But having looked through all the various Ethereum nodes/client's code there is often a Signaling Server or Relay nodes with ports exposed to external network involved.

1. Our current internet infrastructure is geared towards limiting internal ports exposure to external ports the reason for this is Botnets. Ethereum clients and nodes on a network level are technically as decentralized as the next bittorent/limewire/botnet.
2. Ethereum might use state of the art encryption standards but it ignores failures at the most basic levels. Its hard to explain this point but it can be summarized with this video from LockPickingLawyer. https://www.youtube.com/watch?v=PEaIadLDLIA
3. POW vs POS and this debate riles up crypto community/enthusiasts but both methods are essentially Proof of Stake albeit implemented with stakes being either stake or work. Also each method fundamentaly asks person to invest something in exchange for mining benefit. An analogy to this is a News organization whose journalist pay for stories vs a News organizations whose ethics and codes dictate not to pay for stories but simply observe and report.

Again my intentions are not to downplay Ethereum but a constructive criticism on the whole buzz words around blockchain, decentralization and web3. I am in for decentralization but current cryptocurrency enviornment looks more like a charade. Again sorry for playing the devils advocate here.