Here are the pics I showed in the video for one point I made out of the many.
Seeing as the sets are the only thing being mentioned, I will do my best to explain the rest of the points.

***Hybrid Sets***

When it comes to may of the hybrid sets (sets designed to allow a person to effectively use stamina and magicka abilities), they often don't do what is intended or simply don't do enough to be worth it. When it comes to dealing damage in this game, max resources, crit chance, crit chance modifiers, ability penetration for physical and magical, DoT damage modifiers, and raw damage increase through increase magical, poison, physical damage, etc. modifiers all play a factor.

When you look at a set like (https://pbs.twimg.com/media/CySWBDAXcAEOItG.jpg) PA, you see that the stats are going to both sides of magicka and stamina, but split. This ends up doing very little to increase your damage out put. When you look at something like (https://pbs.twimg.com/media/CySWBf3XcAA-sPk.jpg) Curse or Scales, the 5 piece damage is influenced by one set of stats but yet has 2-3-4 piece bonuses designed to make it a middle of the line piece. In the end, these 2-3-4 piece sets are a step in the right direction, but they need to take a page from Molag Kena and give both the stamina side and magicka side in every set piece (ex. Max stamina and max magicka for 2 piece, and things like that).

***Crafted Sets Only In 5 Piece Sets***

There are many sets out in the game that only have 2-3 piece set bonuses and they offer unique abilities and build options for those who want them. Many people who use sword and board or who use duel wield, they have access to using two 5-piece sets, which means they have quite a few more options to builds than a person who uses a staff, 2-h sword/mace/ax, or bow. This problem is especially pronounced with the release of T1 that gave some 5-piece sets some ridiculous damage and/or stats. ZoS could remedy this by adding some 4-3-2 piece crafted sets or make 2h weapons count as two pieces (may need to reduce the stats a little bit).

***Can't Change The Style of Gear***

When it comes to making gear, you only have to make it once and you're pretty much done until level increases or some ridiculous trait comes out that is way better than the one you have now. This is good as it doesn't drain resources, but what about motifs? Plenty are released every patch and people spend many hours farming them (and making videos about it, in my case). When you are done farming these motifs, there is really no use for them as you already crafted that TBS set during the release of IC. Unless you are leveling a new guy or are making the same set of gear many times over, you'll never get the full use out of a motif. It kinda makes motif grinding pointless. To fix this, they should do something similar to the Imperial gear conversion that the Imperial Editions gives you access to. For example, you go to an anvil, tailor shop, etc. and you use the new style gem and some resources to change a style of gear to whatever gem you put in.

***No Jewelry Crafting****

This is a pretty self explanatory issue. With the release of T1, pretty much every set in the game that have a 5-piece bonus comes in jewelry; that is, every dropped set. Crafted sets are somehow still without a jewelry counterpart, even though it has been ages and the crafted sets are not even ridiculously over powered. This is more a less a quality of life improvement as allowing people to craft jewelry would making grinding a little more forgiving as long as you got 5 pieces of a set that had decent traits, you would be able to craft a set around that to fill the holes. This would take some of the edge off grinding and would make leveling a little more interesting, as well as offer some new build paths late game.

***Crafted Sets Are Made With One Armor Type In Mind***

What I mean by the title is that when you look at sets like Morkuldin, you notice that every piece bonus is for a stamina character, but yet you can craft the set in heavy and light? When it comes to many of the sets that you can craft, they were not designed to be flexible with all the armor types and this really limits what sets can go with what armor type. Why give the player the option to craft a set with one armor type in mind in some other armor type? Seems rather pointless or poorly thought out.

What ZoS could do is allow the player to manipulate the stats or set piece bonuses to something we would use. Maybe the use of a arcane forge to change Morkuldin to summon a fire staff as opposed to a sword. They could also use the three stations around the world and make one for one primary stat. With three crafting stations in the world, they could do all three stat types. This would also have the added bonus of making exploration more worth it.

If I missed any point or if you want a full argument, the video mentioned at the beginning is a great option to listen to.