I learned from reading a bike magazine back in the late 90s, when the Harley came out with the TC88, that Harley knew very little about how the engine worked, especially with regard to engine oiling and crankcase ventilation. They had been building them that long, and they worked, so they left it alone. But when they tried to do a major redesign on it the the TwinCam88, they did some changes and things didn't work properly. Aside from crankcase ventilation, and oiling problems, the couldn't even get it to shift. It took several engineers 2 years to figure out the problems. I don't remember all of it, but it wouldn't shift because it was too smooth. The old EVO shook so much that the shaking/vibration had actually assisted it in shifting. I do remember that they had to add new oil galleries and crankcase vent tubes to make it perform properly, than after all that they still had a cam chain tensioner that tended to blow up at 30,000 miles.
I think before engineers (yes they can make mistakes too) redesign something they should seriously study what that have, especially when the last redesign was over 60 years ago. There should be some way to get all the oil out. you can even do that on a Harley. Of course a Harley is a lot more modern and made better out of better materials than a a new UCE Enfield. A modern H-D is a 100,000 mile+ engine, even at freeway speeds, as long as you keep that can chain tensioner replaced.
I would love to see a couple of modern motorcycle engineers carefully examine the new Royal Enfield engine. and issue a report. I know I bought it because it is old and outdated, and wouldn't be attracted to it if it were not noisy and made a lot of vibration, and looked like a Honda (make that a Suzuki, their S40 is the most modern styled large Japanese single, and it dates back to 1986. The XR650L, DR650L, and KLR650L are designed as dirt bikes, not street bikes. However, you might want to try the new Yamaha SR400. It is an air cooled single cylinder that dates back to 1978. It was here even before then, having been pulled from the TT500 dirt bike. Even today's version lacks an electric starter, which makes me believe me I might get a good deal on one here in a year or so, when they don't sell. Unfortunately you are stuck with FI on that one, and no way to start it when the battery goes dead. And it's FI will be turned for emissions, not for performance. But it should be a reliable bike, should be capable of over 100,000 miles of freeway use. It just doesn't look, sound, or feel like a 50+ year old British bike. Anyone else here just love that "chug chug" sound that happens after you shut the ignition off? That big piston just don't want to stop as soon as the ignition is shutoff. This is truly a bike where you shut the engine down, not turn it off, like with an electric motor. Even with an expected engine like of 50,000 miles, I expect to get my moneys worth out out, in pure fun. Unfortunately, most people are looking for exactly the opposite of what the engine delivers. They want smooth, quiet, reliability. no need to tinker with the air/fuel induction, just hop on, hit the magic button, and ride for say, 100,000 miles or so, with no involvement between them and the bike.