I am not with Laminar Research; just a flight simmer. I don't have any association with any other business linked with my comments below.
X-plane 11 has a tendency to be resource hungry over and above X-Plane 10. Have a look at the following link at https://www.x-plane.com/kb/x-plane-11-system-requirements/ Although your system "fits" the minimum requirements serious flight simmers build a purpose built PC equal to or with greater specifications than the recommended specifications. Personally I think your weakest link is the graphics card with only 2Gb of VRAM which contributes to the low frame rate. A purpose built PC allows you to upgrade components as and when necessary or when affordable
Because X-plane 11 is resource hungry good cooling is required to cool the graphics card and the CPU. Does your system have cooling? If not you may or will experience crashes when flying due to overheating.
Also have a look at the following link at https://www.youtube.com/watch?v=Tvp8C0rPAuw This video may also help as well in answering your question. The author, Michael Brown owns a company in the USA that builds purpose built PCs for flight simulation especially for X-Plane. Laminar Research recommends this company as the supplier of PCs in the USA.
When X-Plane was first released there were comments in this forum whereby Mac systems were experiencing problems with AMD cards. NVidia cards give a better performance. Because your system has some "age" this may be a contributing factor as well.
I hope this helps in answering your question. Others no doubt may have a different view.