The LCP of a website is determined by several factors.
First of all, LCP is basically how long it takes the browser to load the main content of the Webpage after getting the first byte from the server.
Which means it could depend on:
The size of the html itself (ie how many DOM elements are there)
The quantity of external resources in the <head> section (css, js etc).
The quantity and size of images
Basically, you need to dive deeper into your page content and see if there is a bottle neck.
1 thing I like to do is always to compress images and also reduce the physical resolution of the image to match the space they will be displayed in.
Secondly, use as few external css and js files as possible. Libraries/Frameworks like Reactjs and Angular will actually combine each file to 1 huge file during deployment. This is preferable because a single 100kb file is much much better than 100 1kb files (This has to do with the overhead that comes with HTTPS and TCP per request). Similar to how copying 1000 1kb files to a flash drive is much more slower than copying a single 1 mb file.
Those are the ideas I can give offhand without analyzing the website myself