Installing LiteSpeed Cache and leaving every setting on default gets you maybe 20% of the available speed gain. Here's what changes when it's actually configured.
What "just installed" LiteSpeed Cache gets you
Default settings enable basic page caching — HTML is cached, repeat visits load faster. But CSS/JS delivery, image optimization, object caching, and database cache warming are all off by default or under-configured, which is why sites often see little to no Core Web Vitals improvement after just installing the plugin.
What changes with proper configuration
Object cache (Redis, where the host supports it) cuts database query time on dynamic pages; CSS/JS optimization directly addresses LCP and INP; image optimization + lazy load exclusion above the fold is the single biggest CLS fix on most Elementor sites; cache warmup/crawler pre-generates the cache instead of the first visitor paying the slow-load cost.
A real before/after
On a typical Elementor Pro site with 15-20 sections and 3-4 third-party embeds, going from "installed, defaults" to "fully configured" LiteSpeed Cache typically moves LCP from the 3.5-4.5s range into the 1.5-2.5s range — the difference between failing and passing Google's Core Web Vitals threshold.
When caching alone isn't enough
If the underlying page is genuinely bloated (unused CSS, unoptimized hero images, unnecessary plugins each loading their own scripts sitewide), no cache configuration fully compensates. Caching hides load time on repeat visits; it doesn't fix the first-visit cost, which is what Core Web Vitals actually measures.