In addition to problems with the laptop line, Apple has problems with their desktop line as well. The Mac Pro is too old and expensive, with a 6-core configuration costing 4 times as much (https://pcpartpicker.com/list/xc3LXP) as a custom build one with similar performance and the 12-core configuration can cost 3 times as more than a Threadripper build. The iMac Pro is in a similar situation with the only difference being its all-in-one design. Both are due for updates and they need to have more cost-efficient technology inside or custom built PC’s will overtake them.
The iMac is still stuck on a chassis from 2012 and Intel processors from early 2017. The last refresh was nearly 2 years ago, in mid 2017. In order for the product to be more attractive, it needs to be refreshed as soon as possible. Even then, the price would most likely be too high to be considered viable and people would simply switch to custom built PCs.
Marcus Tech Blog 