I played through the first rank (replays attached).
My general feedback - you have some interesting ideas. I wouldn't call most of these levels easy, actually - most of them would be medium to hard.
The difficulty curve is all over the place, which leads me to guess - are these levels simply kept in the order you created them? Personally, I would advise against this. Make levels first, sort them into order by difficulty later. Even once you've got the order more or less, go over it again and see if anything should be moved. It doesn't have to strictly be a case of "every level is slightly harder than the one before it", but this rank felt like the difficulty was all over the place - levels 12 and 14 in particular were quite tricky, while 15 and 18 were bordering on trivial.
In some places, the visuals feel a bit low-effort. The obvious example would be on the crystal levels, where the blue beams just abrupty end in midair. The pillar on the left on level 17 is another example of this. Or, the one-way arrows on levels 13 and 14, which bleed into the terrain beyond where they need to cover - on level 13 this may have just been intended, but I find it hard to believe the small section of one-way arrows in the pit's floor on level 14 was specifically meant to be there.
There are also parts that are unnecesserially execution-heavy. For example, on level 12 - which is, for the most part, one of the best levels here - at least in my solution, the fall distance from the platform to the builder bridge below is exactly the maximum survivable fall distance. If the builder isn't placed pixel-precise, they splat. If the basher is timed such that one lemming steps up onto the rounded part at the end of the tunnel, and thus falls from 1px higher, they splat. This adds nothing of value to the level - it just makes it more frustrating to execute the solution. Level 19 took this to the extreme, requiring syncing up the timing of the crowd together with three worker lemmings - I didn't even bother to actually fiddle around and make this work out, instead I just saved a replay when I had the general idea (but with the wrong timing) and left it at that, because these kind of timing "puzzles" are not actually fun to play; in particular, nothing would have been lost from this level by putting steel along the left wall, so that the basher stops rather than creating a tunnel that goes out of the level, but doing this would hugely reduce the execution difficulty that makes it annoying.
The last thing I'd point out is that a lot of these levels have little more to them than "do you know this trick?". In general, levels that solely consist of a trick but nothing else, are only interesting if the trick is new, or at least very uncommon - but most of these are very well-known tricks by this point, so the solution is immediately obvious to anyone who's played packs a lot. The best kind of levels for experienced players (aside from levels that come up with and introduce a new trick), are levels where the difficulty in particular comes from figuring out how everything fits together - which may include these tricks, of course. I'll explain with an example, which I'll spoiler tag for the benefit of those who haven't played yet.
Easy 20 is a prime example of a level that is really just a "does the player know this trick?" check. The interesting element is that you dig a holding pit, then release the crowd with a bomber falling from the entrance. This is the only puzzle in the level - the rest is just building over a gap. Instead, what could have worked better in order to make a level using this trick, would be to have it look like the bomber and/or the digger is needed elsewhere in the level, but in fact there's no other way to control the crowd, so the player would have to find a different way to handle those other parts.
Overall though - you definitely have a lot of potential here, and the kind of levels you're making at this point do remind me a lot of how my early packs looked (back in the Cheapo days), where I'd have some genuinely really good levels but, in an effort to simply get a massive pack together as quickly as possible, I'd also end up with a lot of boring / generic filler ones. My general advice - keep in mind there's more to a pack than just making levels (in particular, those levels should also look nice, and even more importantly, effort does need to be put into their ordering), and keep in mind the idea of "quality over quantity". It will likely be that some of your attempts to create levels, don't really go anywhere and just have to be discarded - it's disappointing, but it's the reality of level design. For what it's worth, I really do have to say that the quality of this pack is much better than I had expected based on how frequently you're releasing packs and the comments about the lack of effort on proper folder structure in your past packs - it may be well worth spending some time playing other highly-regarded packs and comparing the levels in those, to the levels in your pack, to see how you can improve even further.
Just to give you an idea on timing - Lemmings Plus II took me about three weeks to make, with me working on it basically every waking minute at the time. This is, as far as I'm aware, by far the fastest any large pack with a positive reputation has been created. Most large packs - including my other ones - the creators work on them for months, if not years.