I've never liked knotless tapered leaders. Some do work better than others, but a knotted leader works much better for me (and lots of other anglers). For the past couple years, I've tied 7.5' 3X leaders. Most of my fishing is for warmwater species, and I'm using heavier flies. 3X tippet withstands abrasion better than 4X, and smallmouth dive for rocks when they're not leaping.
Here's the twist that makes the 7.5' 3X leader the one I have tied on. If I decide I need a longer leader, I'll just tie another foot or so of 3X tippet on. If I need a lighter tippet, I cut back the 3X, and add a 4X tippet. That extends my 7.5' 3X leader to a 9 foot or longer 4X. Need 5X tippet? Snip the 3X back, tie in a 6" section of 4X, and then add the 5X tippet. I'm using 5X for smaller flies, and perhaps spookier fish, so the extra length I gain is an added bonus. I do tie 9' knotted leaders in 3X and 4X, but rarely use them now.
Another benefit of knotted leaders is that sections can be replaced as needed. I get a wind knot every now and then, and simply replace that section of the leader. If you snag a knotless leader, and break it, you need to determine what diameter is at the new end. That's much easier with a knotted leader.
I read on forums that people get algae, soda cans, dead birds, etc sticking to the knots on a knotted leader. I can honestly say that has never been an issue for me, and I fish way too much.
A couple of years ago, the Delaware River had clumps of algae floating throughout the water. This stuff was everywhere!!!! The only thing that caught any algae was the fly itself. It was so bad, that if you did catch a fish, it was covered with 2 pounds of algae by the time you landed it. I was hooking bluegills, and digging through a basketball-sized clump of salad to get to a little fish in the center!
P.S. I use blood knots on all sections of knotted leaders, even the tippet. A properly tied and TRIMMED blood knot is just a smooth bump.