An exercise is functional when it has a clear role in relation to the person's goal, abilities and context.
A program needs a clear measure of progress
Without a clear criterion, it is difficult to know whether you are progressing. It may be better technique, a greater range of motion, more high-quality repetitions or a heavier load with the same level of control.
Fatigue is not the main measure of quality
A hard session may be appropriate, but feeling exhausted does not prove that the program is well structured. High-quality training leaves enough room for recovery and the next stimulus.
Simple exercises can be highly demanding
When tempo, load and technical criteria are set well, fundamental movement patterns often provide everything needed for long-term development.
What to do next
Observe how abilities developed outside your main activity transfer into your everyday performance. Record your observations and use them as feedback for the next program adjustment.