A 3 year old cheap laptop can certainly feel like it has slowed down. Often the cooling design of them is poor and if dust has built up the thermal protection will throttle the CPU to protect it. This is on top of usual bloat and disk fragmentation etc.
A proper clean up, SSD, memory upgrade and fresh OS install can work wonders, but given that it probably has a cheap and nasty screen and keyboard why bother?
A decent laptop will have a screen that is good to look at, and generally nicer to work at. IME a £1k laptop will outlive several £300 laptops, so if you can afford a decent Dell/Apple, whatever, then you won’t regret it.
Laptops are now pretty much like kitchen white goods, you get what you pay for.