Stress tests are conducted to determine if the resources allocated to your website are sufficient. Based on the stress tests, it appears that your server is unable to handle a high volume of requests.
I’m not sure what others are saying about the ideal or minimum requirements for WordPress to function well. However, based on my experience with clients, a minimum of 4 GB of RAM, 4 vCPU, and 2 GB of swap (although I prefer 4 GB as well) is needed for their websites to perform well.