"Slow" can mean a lot of different things, and the right call depends on what's actually causing it rather than just how old the laptop is. Here's a practical way to think it through.
Work out what's actually slow
Sometimes a laptop is slow because it's cluttered with unused programs, background processes and years of accumulated junk — that's a software problem, and it's usually fixable without replacing anything. Other times the hardware itself genuinely can't keep up any more, particularly if it's still running on a traditional spinning hard drive rather than an SSD. A proper diagnostic will tell you which one you're actually dealing with.
When an upgrade makes sense
If the laptop is in otherwise good condition, upgrading to an SSD is often one of the most cost-effective ways to bring an older laptop back to life — it's frequently the single biggest bottleneck on machines that are a few years old. Adding more RAM can help too, depending on what you use the laptop for. Both are generally far cheaper than a new machine.
When replacement makes more sense
Replacement starts to make more sense when a laptop is many years old, when the battery and other hardware are failing alongside the slowness, or when current software and updates have simply moved past what the hardware can comfortably handle. At that point, an upgrade is often just delaying the inevitable rather than solving the underlying problem.
Don't forget your data
Whichever way you go, make sure anything important is backed up before any work happens — that applies whether you're upgrading the existing machine or moving everything across to a new one.
The short version
If it's software clutter or a hard drive holding things back, it's usually worth fixing. If the hardware itself is genuinely past it, a new machine will likely serve you better than throwing money at an old one. A quick diagnostic will tell you which situation you're actually in.