First of all, understand that there is no way to tell of a truth, or be sure that ordinals, runes and so on, were introduced by miners to increase bitcoin fees, there is no way to be sure about this.
But then, even if they did, bitcoin is still decentralized because those project being launched on the bitcoin blockchain are actually independent on their own, this means that, the miners sure have to promote the project to a lot of investors, who carry out alot of transaction on the bitcoin network, to result in a clog of the mempool which brings about the high fees.

It is just same as in 2019/2020 when cryptokitties shut down the ethereum blockchain due to a lot of people participating in the game, if miners launch a project on the bitcoin network with intent to increase fees, if no body give attention to such project, fees won't increase, it's as simple as that.

Yes of course, the high fees means, mining is profitable for miners, and this encourages them to stay, and others to join, the more miners on the bitcoin network, the more decentralized the network becomes, and this also makes bitcoin a good digital cash to completely trust.