I like yarns with more plies Fine2-ply and singles can knit into a nice fabric, when they are knit on fine needles. And very fine 2-ply knit on very fine needles produce a wonderful fabric.
I certainly knit a great deal worsted weight 2-ply yarns, into fabrics that I thought were nice at the time. I knit a lot of Lopi. I did these things because there was a class of knitters with experience in knitting such things that told me it was a good thing to do. It was. It let me learn from my experience, and learning is a good thing.
Lopi has a lot of fans. Garments knit from Lopi have a particular aesthetic. Lopi yarn is easily and inexpensively produced. (e.g., less effort is put into combing, and less energy is put into twist). And, objects can be very rapidly knit from Lopi. However, the resulting fabrics are heavy for their warmth. That is, a gansey weighing less than 2 pounds will be much warmer than a Lopi sweater weighing more than 5 pounds. And the gansey can be tailored to flatter the figure, while the Lopi simply hides the figure giving the appearance of bulk. That is good, if you want to look big and bulky. On the other hand, my favorite aunt wore pink Lopi socks almost continuously (day and night) for the last 12 years of her life - all knit by yours truly. The other thing about Lope is that it is not as durable as some other fabric constructions. For example a Lopi sweater will not last as long as a gansey knit from 5-ply. And, an Aran sweater knit from 2-ply will last longer than a Lopi sweater of the same weight and warmth. However, an Aran sweater knit from the same weight of wool spun into real 10-ply, will be much warmer, and last much longer. And the 10-ply (or 10-strand cabled) yarn can provide an elasticity that is simply astonishing. It can be weatherproof, without being stiff.
I knit a lot camping, hiking,sailing and ski gear for myself and friends from 2 and 3-ply yarns, mostly MacAusland. When I started knitting, my ski buddies, all told me that hand knit woolens were just worthless in the cold (i.e., snow camping) . I convinced them that hand knit woolens could be warm by giving them hand knit objects knit from 2-ply that were very warm and durable. I know 2-ply can be knit into good fabrics. I have no regrets knitting all that 2-ply - the objects were better than what I could get commercially. However, I do wish that I had discovered the virtues of more plies, sooner. (I still have many pounds of MacAusland, and I still knit it.) However, the objects that I knit today from yarms with more plies are better. The objects knit from yarns with more plies are warmer and more durable.
My point is that yarns with more plies can be knit into better fabrics. And as spinners, we can make better yarns. It takes some effort, but we can make lighter weight yarns that are just as warm as heavier weight yarns, and which are much more durable. And, they have better drape. As hand spinners we are not so concerned with the cost of inserting more twist. Our hand spun does not have a price point. We can afford to make better yarns.
Alternatively, rather fine (2,500 ypp) 2-ply ply yarns can be knit on rather fine needles (1.4 mm) to produce wonderful fabrics. Everytime I make this fabric, I am just amazed by it. The yarn is easy to spin. and it is only 30% more stitches per inch then gansey fabric so it is not that many more stitches, I knit the fabric soft, so it is not as much effort, and minimum stress on the hands. It can be easily produced with either a knitting belt or a knitting sheath, I also make a 6-strand cabled yarn at ~1,600 ypp that I knit on 1.7 mm needles to produce a soft, warm, durable fabric. It is a little thicker, warmer and more elastic fabric.
I am not talking about the weatherproof, industrial fabrics that I knit for sailing gear. I am talking about soft fabrics that will remain beautiful for many wearings.
Now, I am sure that there are a lot of (experienced) knitters that will think that my views on more plies is silly. That is OK, those are the same knitters that did not tell me that the easy way to get a weatherproof knit fabric is to use finer knitting pins. I put in a lot of effort and wasted a lot of time working this out for myself. They could have said, "Oh, it is easy, just use finer needles". However, they did not.
At this point in my knitting career, my rule of thumb is that more plies in the yarn and finer needles produce fabrics that I tend to like better.