Bitcoin already had 2 major upgrades - SegWit and Taproot, and more will be coming in the future. Bitcoin doesn't need to radically change, like adopting PoS, for example, because it already works great. Bitcoin is decentralized, and it is its greatest achievement, there's no coin more decentralized than Bitcoin, and you don't want any centralization on a network that holds hundreds of billions of value.

I think Bitcoin could "change" meaning adopt a hard fork if it was necessary, like if some unforseen circumstances demanded the change of mining algorithm or block rewards. But so far it's not needed.