Training should be challenging and varied and get you out of your comfort zone. You don’t want to get to comfortable in your workout, you need to push that little extra to get fitter or better on what you do.
Just fluffing around in the gym is nice and you can possibly maintain what you have, but you probably won’t develop that much.
Therefore, variation in exercise is extremely important and to challenge yourself. However, even though I think it’s good to try different new exercises and constantly seek challenges it’s important to not forget about the basics!
It is better to vary the workout with the basics and increase/ decrease weight, work eccentric, increase / decrease reps, superset, triset and combining them with other exercises. In this way you can find a good variation and still get to develop your skills in your basics.
Let’s say you want to be better/stronger in squats, then you must of course practice the squat! If you do to much of vaiation of everything else and miss out on actually working on your squat, you will probably not develop any greater skills in squats.
I think there is exercises that are extra important to actively work on every week. Work as a single exercise or combine with other exercises, but don’t exclude them.
My week always contain squats (back, front or overhead), pull ups, deadlifts and shoulder presses (And for my sport specific training the snatch and clean as well).
I can of these 4 exercises build several varied and challenging workouts without missing out training my basics.