WordPress can be a gift out of the box. You get a pre-structured, search-engine-friendly site, a huge library of templates to move fast, and endless ways to customize.
Plenty of the owners I work with run WordPress, and almost every one of them opens with the same line: "why is my site so slow?" Nine times out of ten, the answer comes down to a few things.
1. Too many plugins
The trouble with WordPress plugins is the same as hoarding apps on your phone. They are one click to install, built and maintained by all kinds of third parties, and wildly inconsistent in quality. I regularly open a simple site and find fifteen plugins active, half of them not used by anyone. The rule is simple: if you are not using a plugin, remove it. You will see the speed come back almost immediately.
2. "All-in-one" optimizer plugins
There is a whole category of all-in-one super-optimizer plugins out there, and most people install them because they sound fantastic. They took the bait. I almost never recommend these bundles. They dig deep into your installation and, more often than not, drag performance in the opposite direction of what the sales copy promised. When a site is slow, my rule is the opposite of a bundle: keep the installation clean, lean, and specific to what you actually need.
3. Oversold shared hosting
Overselling is when a shared host advertises huge disk space and bandwidth that is spread across the whole shared network, not reserved for your site. If every site on that server hit its limits at once, the whole thing would crawl. The big-box hosts are known for it. Cheap hosting is fine to start, but when you get serious about speed, move to something self-contained like a VPS.
4. WordPress running errands on every visit
WordPress has a built-in scheduler (its "cron") that fires background tasks, checking for updates, running backups, publishing scheduled posts, on visits to your site. Stack up enough plugins and those errands can run for a big chunk of the day, dragging the site while a visitor is trying to use it. A developer can move that scheduler to run once, quietly, in the middle of the night instead of during business hours. It is a small change that often makes a noticeable difference.
Keep it clean, keep it lean, put it on hosting that is actually yours, and stop it from doing chores while customers are watching. That is most of the battle.
Developer's advice
The fastest win you can do yourself: run your homepage through Google PageSpeed Insights, then compress the biggest images it flags with a free tool like TinyPNG. Oversized images are the number one slowdown I find, and you do not need a developer to fix them.