I can see this from 2 different perspectives...
As consumers, we always ask for more and faster. Manufactures give the consumers what they want. Intel designs a chip with a rated TDP yet said chips run at higher TDP's. Manufactures try to save a buck and reuse what they can.
We are dealing with an extra 2 cores on the 2018's and 4 extra hyperthreaded cores. They are gonna run hot under load. However, just having to return 1 MacBook Pro due to excessive heat/fan/battery issues, I can see why people are getting so upset. I have had in the past 2 months, a 2017 i5 13" TB, 2017 i5 nTB (wife's), 2018 i5 13" TB, (3) 2018 i7 2.6 15" TB's. With all those systems, I only had issues with 2. My wife's nTB model fans pretty much ran constant until I did a complete reset and did not use her previous backup. After that it was quiet as ever. The 1st 15" I had I sent back due to Amazon not price matching another store (talking $450 difference), but had 0 problems other than 1 KP before both updates. I was really hesitant at first on giving it up but the savings couldn't justify keeping it. The 2nd one I received same configuration had MAJOR issues with heat, temperature spikes, fan noise, a battery that would never fully charge, and some strange graphical glitches (should have known something was up with it on Saturday when I did About This Mac and it showed the Radeon graphics in use doing nothing). Bottom was hot as hell. I tried resetting it, resetting the nVme, SMC, nothing changed it. Exchanged it yesterday, and this 1 performs like my first one, with idle temps around 40-42, and while surfing in the 50's, sometimes occasionally 60's. Under Cinebench mid 90's. Fans only kick in when needed.
I think a lot of this has to do with the lottery of your machine, who built it, what day, etc. I can almost guarantee you if I would have taking apart that 2nd 15" I would have found either to much TIM, not enough, or something not making contact. My 1st XPS 15" last year came like that. When I took the heatsink off it looked like someone bathed in TIM. After reapplying TIM, temps dropped 15-18 degrees! I just don't think the quality is still up there at the Apple assembly plants.
It really sucks that people are dealing with these issues, especially on such expensive computers. For the cost of these laptops, they should be white glove! However, I will say this, and this is not just an Apple issue. Its an industry wide issue. My wife did not like the Mac and wanted to go back to Windows. I returned her Mac and bought her a Lenovo YOGA 920. Awesome system, i7 8550u, 16G DDR4, 1TB SSD. System was fast, well built. BUT, the fans stayed on constant, with temps around 40-50 doing light tasks, and 90's doing heavy tasks. She hated the noise, so I returned it (so glad my Best Buy is awesome). This time made her go to the store. Salesperson sold her on the Surface Book 2. Really nice system. I actually really like it. 13.5", i7 8650u, 16GB LPDDR3, 512GB SSD, and the nVidia 1050 graphics card. Doing basic tasks, again temps in the 50-60's, and heavier loads high 90's. Fans are louder than the Mac's under load. Remember Microsoft is using a custom vapor chamber cooler to! We all want thin, light portable laptops. This is what we get... Funny thing is she doesn't notice it cause SHE picked out this laptop. If I would have came home with it she would have complained and it would have went back lol.
Again, does this make it right? Nope. But we as consumers drive the industry. We tell them we want, want, want. They have ass deliver to make the most profit.