Not sure if you have noticed but the node count has actually increased over the last year, disproving your theories of node centralization.
Recording all transactions on a single ledger is part of what defines Bitcoin, it had its critics even when Satoshi was still around. Many of the people within Core do not believe in this original vision, the people behind Bitcoin Classic and Bitcoin Unlimited still do. Bitcoin can scale, regardless of what you say, and if Bitcoin does not scale, what can I say but be prepared for Bitcoin to become the myspace of cryptocurrency. Since most of the alternative cryptocurrencies already have far greater transactional capacity compared to Bitcoin today.
https://bitcointalk.org/index.php?topic=532.msg6306#msg6306Again, total node raised due fake Bitcoin Classic nodes, actual nodes have decreased, mainly because people no longer are forced to run Core to have a wallet, there's tons of other options now, and most people can't be bothered to download the entire blockchain, so the last thing we need is alienate people even more to run nodes by making it more heavy.
Of course Bitcoin can scale on-chain, if you centralize the nodes... pick one, you can't have both. We'll never compete with any centralized solutions all on-chain, this is a fact, I mean who doesn't understand this yet?
If Bitcoin doesn't scale to pay coffees with it for whatever reason, then it still will be a very valuable "Gold 2.0" solution. I would gladly pay a good fee for a technology that guarantees im on a decentralized network backed by the biggest amount of computing power on earth.
I don't need this level of security to pay a damn coffee, so I would use whatever it's out there. Hopefully LN, because it will be infinitely times better than anything we have now.
All those altcoins are irrelevant, they would run under the same problems eventually, and they would need to either start centralizing the network, or start applying layers.
It is a false dichotomy to say that we either scale or we centralized the nodes, this choice exists on a spectrum. Sure we do increase the centralization pressure on the nodes when we increase the blocksize limit but there are other benefits to this that need to be balanced on the whole. Making Bitcoin more attractive for mass adoption can actually further increase the node count because there will be more people that actually have real reasons to run full nodes themselves, it should be a balancing act, restricting the growth of the network now is a grave mistake.
Your "Gold 2.0" scenario will not come about if Bitcoin can not continue also being a currency, and even if it does then you can have a small community that believes in this while Bitcoin becomes completely obsoleted, out competed and overtaken because other alternative cryptocurrencies can do both as was always the intention with Bitcoin. Bitcoin will become a small niche cryptocurrency for people with this peculiar ideology.
I think Bitcoin can increase the blocksize now, therefore it is not a problem for the alternative cryptocurrencies to do so, however even if you believe that this is impossible, or it leads to dangerous centralization, which I disagree with obviously, alternative solutions do exists, like incentivized full nodes and self funding blockchains. Among many more possible innovations. You might be blind to the competition but I am not.