Yup, it does seem like your issue is just how old the machine is. Using another skin for the GUI won't fix that. The minimum requirements are basically just bare minimum for the thing to run at all, but that won't be considered enough to run smoothly. You would want the recommended specs for that.
@BenRK has a very good point though. Putting the OS and software on an SSD suddenly makes everything so much faster(some reality, some illusion). Not only is the spinning HD much slower than an SSD, but that machine comes with a slower one than the 7200RPM HDs that exist. Even on that slow machine, I'm sure the hard drive is bottlenecking plenty, and switching to an SSD would most likely make the bottleneck the CPU. And I wouldn't be surprised at all considering the rest of the specs if an SSD doesn't get rid of most of your hiccups. The CPU is pretty low end, but usually when it is the bottleneck(as opposed to the HD) you are working fast enough.
Also mentioned, you want to have as little else running as possible, as you only have 4GB or RAM, a good portion of which is taken up by Windows 10. A media player blazing out MP3s is likely much better for you than Chrome with a Youtube video up(just as an example). Another thing where the SSD swap can help, if your system is paging RAM onto that HD, is making that page-file access much faster. Generally, if you run out of RAM, Windows will make a page file on your storage(HD, SSD), which serves as additional RAM. Of course, even on an SSD, that is much slower than the hardware RAM, but it will be much faster on the SSD than on the HD for sure.