On 30 November 2019, the Monero blockchain underwent a hard fork that saw a new algorithm being used. It's new algorithm is called RandomX and has built in features to discourage (or eliminate) mining on GPUs, which are generally only available for those that can afford expensive ASICs hardware, and deployed on mining farms.

Instead, the RandomX algorithm favours CPU mining, meaning more people can mine, as CPUs are available to more people. This allows more to benefit from mining. Additionally, a few million small CPUs and GPU miners, distributed so the network cannot be hogged, means that there is no single weak link or node that could be used or targeted to compromise the network.

To upgrade your mining, or to start mining Monero, I will suggest the xmrig CPU miner

https://github.com/xmrig/xmrig/releases

Download and uninstall the binary for your operating system, or if you wish, get the source code and compile the miner.

xmrig is supplied with a sample json configuration file. The most important information to change is the mining pool you belong to. I use minexmr  https://minexmr.com/

You can also make use of the configurtion wizard https://xmrig.com/wizard