The (LCP) measures how quickly the main page content appears after opening a webpage.
The LCP milestone marks when a website visitor can see the main page content. The faster this happens, the happier your visitor (and Google) is.
It plays a significant role in the mobile version. If the mobile version takes longer on a few visits, then Google stops sending visitors to that page. (That eventually reduces the CTR and you lose a lot of business because people takes action when they use their mobile phone)
The Largest Contentful Paint is one of the three metrics that Google uses as a ranking factor.
According to Google
The overview page of the Core Web Vitals report breaks down the data by the device used to view the URL (Mobile or Desktop). Data is grouped by URL status (Poor, Need improvement, or Good), where the status is that of the worst-performing metric for that URL group.
Open the report for a specific device type to see more performance data.
How to find the Pages that need to be optimized?
Open the search console and check the “page experience” and “core web vital”
Click here and list all the pages that need attention.
How to fix Group urls and the details guide
Fix the “Serve images in next-gen formats” by optimizing images
(Eliminate render-blocking resources)
Use these Plugins for “(Eliminate render-blocking resources”
My recommendation to Fix LCP Errors:
Fix all those pages with plugins and images and see at least 3 weeks to check the movements.
If that still not perform well, then I would recommend consulting with a technical SEO expert.
Because maybe your current page layouts aren’t performing well on mobile devices.
A professional can tell you what exactly the problem is.
I think all the templates have different layouts. You can still keep the same design and just change the layouts that are much better for the mobile device.