I’ve said this a couple of times, but because it suits my prejudices I think it deserves its own post.
Recycling material is fine so long as the material is good. And often it is good, especially when it’s a more formalised, expected component like a transformation or combination or launch sequence. I don’t mind watching goodness several times. In my better moments, I rather like the idea of watching goodness several times.
Furthermore, stock footage has a certain reliability. However dull the rest of the episode is, at least I can bank on the manly combination to be great. This is an efficient way for animators to spend money and time.
And if you’re not convinced that repetition has its place, consider the two most commonly recycled elements of your standard anime episode, which we all take for granted: the OP and the ED.
(Would I take much the same stance on grander kinds of re-use, like repeatedly using the same premise? Of course I would. Of course.)
Animanachronism 
Final Fusion, approved!
Always already approved.
It’s amusing that a show with such a cavalier approach to minor things like physics had a relatively sophisticated set of checks and balances controlling its superweapons.
Heartcatch Precure comes to mind.
I can’t think why.
Speaking seriously, in some ways HCPC needs this defence less than many other titles.
Frame recycling is a necessity for long-running shows and most sports anime abuse it. But y’know, it works, so I’m not complaining.
I never understood people complaining about Utena’s stock footage abuse. It was actually one of the show’s strong suits.
There’s nothing per se wrong with stock footage, the problem is always when the rest of the show’s awful or the stock footage overshadows everything else.
Utena made it work because it fitted with the ritual aspect of the series – on the other hand I watched a bit of Groizer X a while back and one fight literally had the robot launch (a good 2 minutes of stock footage), transform (20-30 seconds) do one thing, transform back to its original form (with the original footage just reversed) and finish off the enemy with one shot.
So basically it’s the execution. Not simply the existence.