Do that many of you actually use the 11, 12, 13 cogs with a 50T front? Question not a challenge. I can't turn those cogs. For me, the problem is that the 2-tooth gaps occur exactly where my "home gearing" is on the flats. Again, for me, that is 50T with the 19T. I like a close ratio cassette where my preferred cadence is spot on. So, I built my own cassette out of a 11-30 and a 14-28. (11 speed groupo) Wound up with a 14-30 that works great. And lots of 1 tooth gearing changes right in the middle of my sweet spot; 14 through 21.

Can I spin out occasionally with a 50-14 combination? Yes, occasionally; but that is at 28 mph; rare for me. I guess we all have different strengths, riding styles, outdoor conditions, etc. My point is that a lot can be done on the cassette end of things.

If you have 11 speed 14-30, it would help if you listed the actual cogs that you have arranged.

It's really difficult to tell what you're actually asking about. Looking at Shimano cs-r8000, if you have an 11 speed cassette (not sure if you do) I don't see how you're missing the 18t that you want. In fact if you mixed 14-28 with 11-30, you'll get 14-15-16-17-18-19-20-21-24-27-30
and if the 21-24-27-30 is too big of steps for you, then you could use the full 14-28 as originally arranged 21-23-25-28
And if you don't have a low enough gear then you could change the 36t inner chainring to a 34t or 33t depending on the BCD, but that's also only a 6-9% drop, but enough to make up for the 7% increase from 30t to 28t of the last position cassette.

Or if you're stuck between 17-19 and want to be in 15-16-17, then that's a 12-13% increase in the cogs, so you'll have to drop the 52 chainring to a 46 to drop 13%.

If you have something different or I'm completely misunderstanding and you have a 12 speed cassette, you can get the Miche cassettes which will let you choose the 18t that you want.

https://cimg7.ibsrv.net/gimg/bikefor...cde2585059.jpg

https://cimg5.ibsrv.net/gimg/bikefor...82a46d117b.jpg
https://cimg8.ibsrv.net/gimg/bikefor...2250919db4.jpg

I use the 12 and 13 with a 50 ring pretty regularly - usually with a tailwind or anything more than a slight downhill. I run 10sp 12-25 cassette (12-17, 19, 21, 23, 25) most of the time I’m in the consecutive sprockets in the middle of the cassette.

I use 50x11 all the time, however I'm riding 20"/406 tires, and that's my highest gear of about 85 gear inches. On my old 700c road racing bike, I think my high was 52x13, I don't think I would ever need 11. On a long gentle downhill, pedaling as fast as I could, I topped out the speedo at 64 or 65 kph (40mph), that appeared to be its limit. Once I got away from flat land and into hill country, the best thing I did was put on a road triple crank, which I swapped from a bike I picked up cheap, for my 52/42 Biopace double, then resold that bike. The triple happened to be half-step-plus granny, I didn't need the half-steps, just that granny low.

Yes. I have 14-15-16-17-18-19-20-21-24-27-30. I did this versus the standard 14-28 for big climbs like Mt. Lemmon. This, combined with the compact 50/34 gives me a lot of flexibility. I ride 50/19 mostly at 17 to 18 mph and do not have much need for the 11, 12, 13 cogs. And with the 34 chain ring, I get some good climbing gears.

I live in flat land Delaware. I have a bike set up as 1X: 6750 crankset with just a 44 tooth narrow-wide ring, cassette is 11 speed 11-34. I love this set up for my area. I occasionally need to get into the 30 tooth cog, almost never use the 34 tooth, but it is there when needed. I have never spun out with 44-11. I have used 46 tooth and 11-36 in the rear just changing to a bit longer of a chain. And I have been in the other direction with a 42 front and 11-36 for riding in areas with some climbing. The only 4 tooth gap is 30-34, then 27-30, the rest is all 2 tooth increments, just fine with a 44 tooth front.