I thought I'd make some comments on GLC 4 since I haven't really seen many people give it very much attention past the couple videos that are floating around and the conversations on Discord. I would do the same for GLC 2 and 3, but it's been too long since I've played either so I don't want to go off of memory or even just watching videos.
I just posted a video of all ten of the "official" GLC 4 levels in normal difficulty, and I'm delighted to say that I have pretty positive reactions. I must admit that I did criticize it a little at first, but I was looking for some video inspiration a couple weeks ago and thought that I should give the mod a fair chance and really put some time and effort into it. I'm glad I did that because there was quite a bit I would've been missing out on had I not spent some time with it.
My favorite part is simply how GLC 4 looks. I remember back when you were showing off previews of the levels on Discord and there were a plenty of compliments from a handful of people, and for good reason. This game looks beautiful, and it's easy to appreciate how much effort went into each level. The medieval theme went very well with the textures used, and I must give some extra love to the two pagoda levels (especially Oriental Swinging Slicer) because they were so well done given that the high-standard for a "beautiful" level nowadays seems to be a super-detailed nature of construction-themed level for PQ.
The only drawback when it comes to just the visuals is the game's performances drops quite a bit, just like Invictaa said. I'm fortunate to be able to play and even record in 1080p on each level, but not everyone has the computer that I do. If I had thought about this while I was beta-testing the mod, I probably would've suggested adding some form of low-detail mode, if that's even possible. God knows PQ could use it lol
There is definitely an argument that these levels are significantly harder than the ones from the previous three mods. The first three levels are pretty mellow and forgiving, but Medieval Dash (level 4) is when things really ramp up, which is honestly okay (although having it be a speed-based level makes that harder). I didn't spend more than a couple hours on any of the levels after that, which is partially because of my skill level but partially because I was able to figure out how each level worked. I thought none of the levels were unfairly difficult to the point where it was like a kaizo level, but that doesn't mean that they do take time to beat.
The commonality in basically the entire second half of the game (so levels 6-10) is everything is based around moving platform cycles, which can make things frustrating for both casual play and speedrunning because there's so much going on all at once, and if you happen to miss a cycle, you end up having to wait a few seconds until you get another chance. I had to pull off a very difficult trick at the end of Pagoda Heights (meaning the entire third floor) because the last set of moving platforms takes (I think) ten seconds to make a full trip. My previous best was 1:02 before I got my 51-second time, and there isn't really any way to get anything in between that because of the moving platforms.
To come back to a lighter note, I hope you don't feel like you're wasting your music on these mods. Regardless of what I might've said in the past on Discord (all I remember saying as I'm writing this is that you often use arpeggios), your songs give the games a very unique charm and atmosphere and there's everything good to be said about that. I've downloaded GLC mods in the past just to listen to the music, and it wouldn't surprise me if others have as well.
Let me poke at a couple quotes:
I have never made a pathfinding level (except Beneath the Waterfall tho), simply because I am just unable/can do it.
Ya gotta start somewhere. I wish there was more to be seen of any of your attempts (beyond Beneath the Waterfall) of a non-linear level because it's difficult to give a judgement on this when there's nothing to go off of. It's not like pathfinding-based levels have to be the most complex creations ever either. Marble Playground is a perfect example; it's an incredibly simple level (two sides, two floors each, a couple linear moving platforms, some slopes, some PowerUps), but still a fantastic level to find a path for. You just need to play around a bit with how big and/or complex you want your level to be. The important part is just giving the player the freedom to do basically whatever.
You guys seem like you want to see how fast a level can be speedrunned instead of how hard a level can be made and still can be beaten.
This seems to be something that was a more common and a lot more appreciated several years ago, probably back to the days of MBP's development and maybe even before that. Levels like TTOTTS, Marble Mosaic, and MPMC all fall under this category, and they were a lot more popular a while back. It just seems like nowadays the "ideal standard" for a "fun" level is one that is easy to play casually and at a fast pace. I'm not quite sure when this shift happened, or why it even happened in the first place. I imagine that a lot of people find enjoyment in both kinds of levels, but we're just so accustomed to immediately trying to beat any level as fast as possible that the fast = better mindset took over hard = better.
But in the contrary, they just ragequitted at level 4 of glc4, which imo is WAYY easier than momentum/conservation of momentum.
You (general) tend to be better at your own levels. You know them inside and out, you're first in line to a lot of the possible tricks and strategies. I personally think the Momentum and Conservation of Momentum are much easier than Medieval Dash for a number of reasons (no moving platforms, almost everything flows very well, not as many chances to have to slow down or stop), but maybe there are some people who think differently.
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TL;DR: There are a lot of things to appreciate about GLC 4, but there are a couple of downsides. Some parts are very good, some are not as good. I understand the confusion and/or frustration that you're having, and I do think people could give the mod a chance and spend some quality time with it, but there still are completely fair arguments on why it could've been better. I had a lot of fun playing the mod, and I will hopefully make the effort to play through the other three games sometime in the future.
Here's the video I made.