The sluggish performance you get is from gnome (the user interface/desktop environment that Ubuntu defaults to). Every 6 months there is an update that noticeably improves things. If you don’t want to wait for it to be totally smother out, check out another desktop environment like xfce or plasma. Try plasma first since it’s got prettier visuals, but I like the simplicity of xfce (honestly, I rather enjoy gnome so use that most of the time)