Strength for development.
How much weight you lift is over stated, intensity wise, because it is an External cue and has no bearing on necessarily on how much exertion you put on a targeted muscle. The goal of any intense workout is to maximally fatigue the targeted muscles and this done by training harder and not necessarily lifting more weight. Getting stronger is only a progress indicator when all other variables are controlled.
By correctly targeting a muscle and executing a rep, you are on your way to more intense training and development. Only when training in that qualitative way does an increase in strength become an indicator of progress.
Seldom does the strength of an advanced athlete keep going up after several years of training. Yet they keep making gains by getting better “Qualitative” results from their workout rather than just focusing on how strong they are.