And this is exactly what happened early in Monero's history, where the lead developer got ejected from the community: https://monero.stackexchange.com/questions/1011/monero-incep...
And this is also what's happening now in Bitcoin Cash, where the developers of ABC (up until now the client almost everyone used) wants to assign themselves 8% of the rewards from a mined block. And the the rest of the community are rejecting it heavily.
So yes, the community would fork it.
And yes, a lot of Bitcoin has been carelessly lost, but these are mostly old cases before Bitcoin had any exchange value. You've probably read about people throwing away hard drives with 1000s of mined bitcoins that ended up being worth millions a few years later. Hindsight is 20-20.
It should also be pointed out that a sizable chunk of Bitcoin is essentially frozen in Satoshi's wallets. Whether to count them into the supply is debatable. Same for Hal Finney.
Further, the massive, overwhelming breakage due to the user-hostile nature of cryptocurrencies has led to staggering deflation. 20% is gone already [1].
Finally, the worst part is that the Bitcoin wealth distribution is worse than any banana republic; 0.00088% of addresses control 17.5% of all coins. 4.11% of addresses control 96.53% of coins. [2] Unless you're a whale, you're fighting for scraps today, and the next generation of market participants will be basically serfs. Deflation and breakage exaggerate this problem.
If you thought letting them eat cake was bad...
[1] https://www.investopedia.com/news/20-all-btc-lost-unrecovera...
[2] https://howmuch.net/articles/bitcoin-wealth-distribution