The longer I lift the more I am convinced strength training should be 85-90% big compound lifts with assitance exercises being only 10-15%. Before I get my fair share of hate mail I do want to say I am not against assitance exercises, they have their place: muscular hypertrophy, weight gain, local targeted muscular hypertrophy, imbalances, stability issues, firing patterns, etc.
Still, several big compound exercises will get you covered for decades. If you look at lifting careers of for example Konstantin Pozdeev or Andrey Malanichev it is usually squat, bench, deadlift and their variations, then some DB flys, back work, hypers. That's pretty much it. And their careers, totals and physiques were awesome.
If you think about it it is very logical. The human physiology recognizes 7 basic movement patterns: squat, lunge, bend, carry, push, pull, rotate. This is how humans have been moving for thousands of years so it only makes sense we train like that, based on evolution, with multi-joint compound exercises which train many muscle groups at the same time in coordinated patterns.
Does that mean that you should only squat, bench, deadlift for the rest of your life? Not really. People forget there are many variations and you may utilize many of them in your training as your main lifts or as your big assistance lifts afterwards.
Examples below:
SQUAT (low bar squat, high bar squat, pause squat, tempo squat, SSB squat, front squat, zercher squat, cossack squat, box squat)
BENCH PRESS (bench press, CGBP, pin press, lockouts, board press, band press, push press, OHP, snatch press, BTN press)
DEADLIFT (conventional, sumo, pause deadlift, deadlift up to knees, block pulls, RDL, SLDL, GM)
The above should be 85-90% of your year-round training and the little stuff rounds up your program based on current needs (local hypertrophy, lagging muscle group, firing patterns (e.g. glutes), unilateral work, core work, stability muscles, etc.). You need only couple of sets a week of these and please do not believe the nonsense you have to hit everything every week. Most of your body muscles are hit by the big lifts anyway, remember?
Example of a 3-week cycle based heavily on the big lifts.
Mon: SQUAT 4x4@70%, pause squats 2x3, core 2 sets
Wed: BENCH PRESS 4x4@70%, OHP 3x5, DB rows 2 sets
Fri: DEADLIFT 3x4@70%, hypers 2 sets
Mon: SQUAT 3x3@80%, pause bench press 3x3@65%, abs 2 sets
Wed: DEADLIFT 2x3@80%, bent-over rows 3 sets
Fri: BENCH PRESS 3x3%80%, front squat 2x3@65%, GHR 2 sets
Mon: SQUAT 3x2@85%, CGBP 3x5, pull-ups 2 sets
Wed: DEADLIFT 2x2@85%, RDL 2x5
Fri: BENCH PRESS 3x2@85%, SSB squat 2x3
Yep, that little. Try it and let me know.