Xojo 2021r2.1 is using 2.13 GB of RAM on my Mac, that is with the following projects open.
The Ohanaware App Kit.
Energy tracking app (which is running).
IOReg explorer project.
Xojo Shell energy test project.
I only have the default plugins that shipped with Xojo, perhaps having all 3rd Party plugins uses a lot of RAM? Tim has an app that allows you to turn off the plugins that you don’t need. Strawberry Software - Plugins Pro
I specifically only the last version before DesktopControls as it screws up my workflow due to incompatibilities needlessly created by DesktopControls. Perhaps having a version with rectControls and DesktopControls needs a lot more memory?
If you’re not using DesktopControls, perhaps give 2021r2.1 a try?
Realistically, you’re gonna have to spring for a new Mac in the near future as apps and the macOS are only going to use more and more memory.