A slow WordPress site is one of the most common things I get asked to look at. The owner has done nothing wrong, they just added the things a normal business adds over a couple of years, and one day the site takes six seconds to load and the contact enquiries have quietly dried up. So before you rebuild anything, here is how I actually diagnose a slow WordPress site, and what genuinely moves the needle.
It's almost never the one thing you think it is
People usually arrive convinced they know the culprit. "It's the hosting." "It's that page builder." "It's WordPress itself." Occasionally they're right. More often a slow site is three or four medium problems stacked on top of each other, and fixing one of them moves you from six seconds to five and a half, which feels like nothing, so you give up. The trick is to find all of them, in roughly the order that matters.
The usual culprits, in the order I check them
Images that were never resized. This is the single most common one. Someone uploads a 4000 pixel photo straight off a phone and drops it into a banner that's 1200 pixels wide. The browser downloads the full thing and shrinks it. Multiply that across a gallery and the homepage is carrying ten megabytes of pictures it never needed. Properly sized and compressed images, in a modern format, often halve the load time on their own.
Too many plugins doing too much. Every active plugin can add its own CSS and JavaScript to every page, whether that page uses it or not. I've opened sites running forty plugins where a third of them were doing a job another one already did, or solving a problem that no longer existed. It isn't the count exactly, it's that each one is a little tax you pay on every single page load.
A heavy theme or page builder. The big drag-and-drop builders are convenient, but some of them output bloated markup and load their whole framework on every page. A site built to look fancy in the editor can be carrying a lot of weight the visitor never sees the point of.
No caching. By default WordPress rebuilds a page from the database on more or less every visit. A decent caching setup means it builds the page once and serves a saved copy after that. This is usually the cheapest big win available, and a surprising number of sites simply don't have it switched on.
Cheap, oversold hosting. The five pound a month plan puts your site on a server shared with hundreds of others. When they're busy, you're slow, and there's nothing on your end to fix because the problem is the room you're renting. This is real, but I check it last, because people reach for it first as the excuse and it's often not the main offender.
What actually fixes it
In practice, most slow WordPress sites get the majority of their speed back from four things: resize and compress the images, switch on proper caching, cut the plugins down to the ones earning their place, and move to hosting that isn't oversold. None of that is glamorous and none of it requires throwing the site away. I'd usually do them in that order and re-measure after each, so you can see which change bought you what.
One honest warning about the plugins that promise to do all of this for you. A single "speed up your site" plugin can help, but bolting on yet another plugin to fix the problem caused by too many plugins is the kind of thing that works for a month and then fights with something else. Fix the underlying cause where you can, rather than papering over it.
When speed isn't really the problem
Sometimes I look at a site, do the honest assessment, and tell the owner the truth: the build itself is the bottleneck. If the theme is abandoned, the plugin stack is a house of cards, and every fix risks breaking two other things, you can spend more keeping it limping than it would cost to build something lean that's fast by default. That's not always the answer, and I'll tell you plainly when it isn't, but it's worth knowing when you've reached it.
If your WordPress site has got slow and you're not sure which of these is dragging it down, that's exactly the kind of thing I help with. You can see how I work with WordPress, or book a free half-hour surgery and I'll give you an honest read on what's actually slowing it down and what I'd do about it. No sales pitch, just a straight answer.