Money is a network
A money is worth more the more people accept it. That is why incumbents are so hard to displace: everyone uses the dollar because everyone uses the dollar. Among open monies, bitcoin is the incumbent by every measure: holders, exchanges, merchants, developers, hash rate, liquidity, and the attention of governments and institutions.
Why a "better" coin does not overtake it
In money, network effects dominate features. A slightly faster or cheaper coin does not pull people off the one everyone else holds, any more than a slightly better social network pulls people off the one their friends use. Worse, a coin whose features can be improved by its foundation is a coin whose supply can be, too. The thing that makes bitcoin boring, that nothing changes, is what makes it money.
The Lindy effect
The longer something non-perishable has survived, the longer it is expected to survive. Bitcoin has run continuously since 2013 with no downtime, no successful attack, through a Blocksize War, exchange collapses, national bans and four 70%+ crashes. Every year that passes adds to the evidence that it works. A new chain has none of that record, and no way to buy it.
"MySpace"
The usual rebuttal: MySpace was first and lost to Facebook. But MySpace was a company whose product could be out-built. Bitcoin is a protocol with no company, whose "product" is a fixed set of rules and seventeen years of them not changing. Nobody can out-build "has not changed".