Should I always use ConstraintLayout for everything?

I would say ConstraintLayout is more versatile and has better performance compared to RelativeLayout, But LinearLayout has its own significance in android you can specify weights of view using LinearLayout and for complex UIs I would say going with ConstarintLayout is a better option because of its performance and in ConstarintLayout you can specify the view positions, heights, widths, margins and paddings based on screen sizes rather than hard coding the values to fixed dp

https://android.jlelse.eu/constraint-layout-performance-870e5f238100

The above link gives more overview of LinearLayout vs ConsrainLayout performances.

ConstraintLayout helps you to avoid using nested layouts and it causes better performance. it's not wrong to use it for everything but if you know that you are not going to have nested layouts, for example, three Textviews respectively, you can use LinearLayout. ConstraintLayout needs more XML code than LinearLayout for simple structures, and using LinearLayout is better for these situations.