Legacy products like visual studio and photoshop also suffer from age. Those codebases are both over 20 years old and have a gazillion features that customers start to rely on. Add in that and codebase that old will be slower to make changes on then something fresh and you end up where they are.
Visual studio had a UI rewrite to .net about a decade ago.
VSCode is electron.
If they had kept maintaining the old thing maybe they would experience less performance issues, which you say is suffering from age, but actually they threw out the old thing and rewrote on costlier and more recent frameworks.
