Is it true that a coin like Gridcoin is a replacement
No!
It's just another coin that was supposed to deliver revolutionary technology and failed miserably although it had years to show what is capable of as the coin was actually launched in 2013.
But in the end, it was just another out of thousands that will spend in remaining time doing pump and dumps on shady exchanges.
The market is more important than technology?
Technology? What technology?
Everything was borrowed from something else but they've failed to address the most important thing, why use it?
Bitcoin has no replacement, because no coin is decentralized as bitcoin, all of them are a bit not decentralized, but bitcoin is totally decentralized.
What do you mean by that? As much as I dislike shitcoins LTC and DOGE for example ar just as decentralized as BTC.