To ask a very amateur question, why do people think Bitcoin specifically will succeed? Aren't there dozens of coins out there which have fixed some of it's most glaring flaws?
There are also some advantages to being "simple". Competitors (like Ethereum) have more sophisticated features (such as smart contracts) and may scale better. But none are as battle hardened. Andreas Antonopoulos did a great talk "Bitcoin Security: Bubble Boy and the Sewer Rat"[1] describing how the platform has survived what's now ten straight years in the wild, exposed to the continuous pressure of hostile attacks. It's scarred and ugly as a result (with amputated opcodes and inelegant hacks) but he argues those are symptoms of resilience. And it is still being improved upon to adopt new ideas emerging from the space (eg. Lightning, Schnorr signatures) just at a slow and very cautious pace.
I can run (and sync) a full node on regular hardware, which isn't easy for more I/O intensive coins that have accreted a magnitude of order larger blockchain history. The HN crowd might appreciate the more traditional, native-looking UI of its client software over some of the Electron-like alternatives from other coins (which sometimes lack basic features like viewing history). It focuses on doing a few things well, namely being a wallet and sending and receiving units. That will always be a use case for transacting or storing wealth, and if that's all I'm doing, then I'd rather not have any other cruft.
You asked a really good question, and I personally suspect Bitcoin will eventually get supplanted by something else over the long term (as happens with any tech!). At some point the advantages gained from a clean, ground-up rewrite will surpass the stickiness of its global adoption. But I've come to believe that will take a lot longer than I initially anticipated.
We're already seeing vastly improved power efficiency out of alternative consensus mechanisms like Proof of Stake, and its still very early days for this industry and its technology.
While most of my comparisons above contrast Bitcoin to Ethereum (its biggest competitor) you are correct there are oodles of alternatives to pick from. Some purport cleaner tech stacks and demonstrate superior transaction volume scalability (like EOS).
Analysts have said crypto today is reminiscent of the plethora of startups seen during the dot-com bubble. The survivors were companies that hadn't even been invented yet (like Twitter, Netflix, Google depending when is your cutoff) and the boring but steadfast ones (like Amazon, eBay, Yahoo). So if you accept Bitcoin as falling in the latter camp there's some comfort in placing your bets there compared to newer, more "unknown" options.
It continues to function as it set out to be.
Gold is a poor medium of exchange, too, but that has not prevented it from being a satisfactory store of value.
(Yes, I know that gold actually was a common medium of exchange at one time; it was displaced centuries ago by the greater convenience of paper money.)
Some visionary types hoped Bitcoin would disrupt government-issued (paper) money and governments and banks generally. The fact that these hopes were dashed does not mean Bitcoin will not remain an OK place to park money.
Most people would not want their asset prices to swing like Bitcoin's value does.
Satoshi's paper is literally titled, "Bitcoin: A Peer-to-Peer Electronic Cash System", but it's generally considered to have failed at that. (Even most Bitcoin events don't allow you to pay in Bitcoin, for example.)
Bitcoin folks now talk about it as "digital gold" or "a store of value", which is fine, but very different than what it was set out to be.
Meanwhile adoption does continue to rise with apps like https://gethaven.app
I can appreciate how off-chain overlays can allow Bitcoin to achieve transactions at scale. What I don't quite get is why this kind of recentralization[1] is good for Bitcoin. It feels like the endgame may be a kind of "worst of both worlds" solution — no longer decentralized, but still not as efficient as centralized solutions.
Unless: Can Bitcoin users prevent off-chain transactions, to avoid Lightning?
[1] "10 percent of [Lightning] nodes control 80 percent of funds on the network." https://www.coindesk.com/bitcoins-lightning-network-is-growi...
Developers unwilling to focus on on-chain scaling is another (leading to the high fees).
Bitcoin also has a big privacy and fungibility flaw, something that Monero aims to solve.