) I can safely say that My Little Pony: A New Generation was great! 
And here are my random thoughts:
MLP: Friendship is Forever clipshow rankings · 8:56pm Jun 16th, 2020
0/10 - AWFUL (unsalvageable, nothing to be gained from watching it, never should have been made, wouldn't recommend to anyone, completely butchers an important subject/teaches a horrible and downright toxic moral)
1/10 - HORRIBLE/BORING (tedious to sit through, hurts to watch it, a bore, no reason to watch it, whatever positive things about it are tiny and not enough to save it)
2/10 - VERY BAD (slightly less terrible, maybe it had that one character you liked or one/two jokes you laughed at that kept it from being a 1 but still very painful)
3/10 - BAD (the kind of bad where you're checking your watch over and over to see how much time is left before it finally finishes)
4/10 - MEDIOCRE (not awful but not really that good either)
5/10 - EH (average, didn't love it or hate it but you feel like you could've done something better with your time)
6/10 - DECENT (the first positive rating on this list, fine overall, you wouldn't watch it again but you are glad you saw it once)
7/10 - GOOD (enjoyable enough that you'd maybe watch it again in future, had some noteworthy flaws but is overall a worthwhile sit-through you'd recommend to someone)
8/10 - GREAT (a solid, enjoyable episode, very entertaining)
9/10 - EXCELLENT (very engaging, awesome, you really recommend it to anyone)
10/10 - MASTERPIECE (extremely engaging, teaches a valuable moral perfectly, definite must-see for anyone)
A-Dressing Memories MEDIOCRE
Cakes for the Memories VERY BAD
Memnagerie DECENT
Deep Tissue Memories EH
Harvesting Memories BAD
Memories and More HORRIBLE/BORING
OVERALL: 21/60 MEDIOCRE
I'll be completely honest: I put off watching this clipshow mini-series because I just wasn't interested. With the show having already wrapped up, this felt pretty pointless and tacked-on. But with Pony Life coming out soon (either the 18th or 21st), I thought I may as well sit through it. And it gave me exactly what I was expecting: six episodes with very little new material all following the same formula that becomes tiresome after the second/third time:
"Hey, Mane Six member, can you get Twilight to talk about some memories for this memory book while we hide?"
"Sure, Starlight and Spike! Oh, hi, Twilight, can we share some memories while we prepare for your coronation?"
"Okay!"
"Did you know I represent this Element of Harmony?"
"You sure do! You've had some great moments! FLASHBACKS!"
"Yeah, and these moments were great too! FLASHBACKS!"
"So true!"
"Hmm, but I haven't always been perfect. FLASHBACKS!"
"True, but you're still great in these moments! FLASHBACKS!"
"You're right, Twilight! I couldn't ask for a better friend!"
"Me too! Let's hug!"
And if that doesn't fill up 22 minutes, just pad out the rest of the time with a song from a previous episode.
I'm just not interested in clipshow episodes, like, at all. Now the idea of recap episodes, I'm alright with if something unique is done with the formula.
Take The Ember Island Players from Avatar: The Last Airbender, for example, where the Gaang sees the Fire Nation is putting on a show about their adventures in the series and they decide to check it out, only to become angered when they see that it's told from an incredibly exaggerated and biased POV. To this day, it's one of the funniest/best episodes because of the clever spin it puts on the "recap episode" plot while still fitting it into the show's story, mocking theatre tropes and even themselves.
Or The Good Ol' Ed from Ed, Edd n Eddy where the Eds make a time capsule and reminisce on old items from previous episodes. However the only three flashbacks shown in the whole episode are brand new clips from adventures that may or may not have happened off-screen (the time machine, Double D having the hiccups and the Eds making a giant pancake), thus providing us with entertaining new material and not boring the audience by dragging out the episode with stuff they've already seen.
We didn't need six whole episodes explaining how exactly the memory book was made when we could've figured that out for ourselves. If the show staff really wanted to do a reminiscing episode, it would've been much better if this mini-series was only one episode with the Mane Six all sitting around the table after Twilight's coronation, looking at the book and discussing their adventures together. But, like The Good Ol' Ed, the past episodes they see in the book are only talked about and the flashbacks are instead reserved for six different events (seven if you include Spike) that the audience haven't seen before, times each of the Mane Six remembers where they lived up to their element and the flashbacks giving us enough context to understand each situation. Boom, fixed.
But alas, we got these six bland episodes that went in one ear and out the other.
LINKS TO OTHER RANKING BLOGS
Season One
Season Two
Season Three
Equestria Girls
Season Four
Equestria Girls: Rainbow Rocks
Season Five
Equestria Girls: Friendship Games
Season Six
Equestria Girls: Legend of Everfree
Season Seven and Equestria Girls: Magical Movie Night
My Little Pony: The Movie
Equestria Girls: Forgotten Friendship
Season Eight and Equestria Girls: Rollercoaster of Friendship
My Little Pony: Best Gift Ever
Equestria Girls: Spring Breakdown
My Little Pony: Rainbow Roadtrip
Equestria Girls: Sunset's Backstage Pass
Season 9
Equestria Girls: Holidays Unwrapped
Friendship is Forever (you're already here, you mashed potato)
I'll be honest. I didn't bother to watch this clipshow. Not as a deliberate snub against it by any means, or any other spiteful or bitter motive. I simply plain old forgot that it was going to air. And really, I don't mind that I missed out - not necessarily because of the review here, but just because I've never been too shot with the whole clip-show format. They can be done cleverly (like with Ember Island Players as you said, though I'd also nominate the Korra episode "Remembrances" just for the gag with Varrick having the prior villains on the phone together
) but something about this one in particular kinda smacks of corporate mandate to me. I could be totally wrong but that's just me. Clip-shows are usually money-saving efforts and I get the feeling that this set was a way for Hasbro to release six "new" episodes without having to pay for more new animation or voiceover time. 
5286111
Trust me, you're not missing a thing. I don't think the new animation/dialogue in-between clips is even enough to make up one episode.
5286119
That would not surprise me in the slightest.
I only watched the first two episodes. I didn’t bother watching the other four.