Can I fix it with plugins?

Some of your performance and UX issues could be fixed using plugins. This might introduce new anti-patterns though. For example:

• most plugins for inlining critical CSS often only include partial CSS, resulting in increased layout shifts;
• most plugins for deferring JavaScript will result in deferred or delayed JavaScript execution. However, when JavaScript is responsible for the largest elements within the viewport, this may result in a poor LCP;
• Even today, (JavaScript) resources are still bundled by plugins or even platform. This may result in decreased FID.

Moreover, with every new plugin chances are that you are unwillingly and unwittingly increasing the server response time and thus TTFB, pushing back the LCP metric even further. So, when you do choose to fix issues with plugins, keep a close eye on the impact on real user experience and metrics.