Top of the line laptops released this year are all relying on Intel's Core i9-8950HK CPU which is know to run very hot.
The first laptop released with this CPU that got my attention and I eventually bought, was the Dell XPS 9570. This laptop is know to have thermal issues since the last generation - 9560. This year gen didn't changed much, it also throttles, but everything else about it is great.
The second laptop, the Macbook Pro 2018 with i9 is not only late to the party, but also severely throttling under heavy use. It's throttling so much that it under-performs when compared to last generation i7.
You will probably be right to blame Intel and their failure to innovate. Their last 3-4 generation of CPU are just iterations of the old design with almost non-existing performance improvements but better efficiency. i9 was running so hot, even in the desktop version, that I give up buying an new a PC because I didn't want to buy a CPU that required the best cooling you can buy just to run it without any overclocking. I continued to do all my work for almost a year on a mid 2014 Macbook Pro with a 4th generation i7-4980HQ CPU. This CPU is so good that any upgrade to the new Macbook was a complete waste of money when you consider the performance gains.
To add insult to the injury in Apple's case with the Macbook Pro, the problems seems to be the voltage regulator, not even the CPU getting hot. Watch this video from Louis Rossmann to understand why this is bad. The original post on this also comes instructions how to work around this issue, if you happen to own one: Optimal CPU Tuning settings for i9 MBP to stop VRM throttling / Explanation of Apple's Engineering Failure.