It ain't just sanctions. It's also that a lot of their network kit is frankly awful.
A few years ago I was involved with a large rollout of customer premise routers to replace outgoing Cisco kit.
The customer in question had superannuated Cisco kit, mostly 857 and 867 kit. The replacements were Huawei 157 and 169F routers. This kit was clearly intended to look like Cisco kit and function like Cisco kit, without actually being a copy of Cisco kit. It did not however function like Cisco kit. While the outgoing Cisco gear could go from cold to fully functional in less than 3 minutes the Huawei kit would take four times as long. Huawei kit was much more prone to just freezing and needing a reboot. Huawei kit was harder to configure and also had a nasty habit of randomly losing a random liner or two of config for no reason.
I always got the feeling that it wasn't finished. Almost like it was still in Beta. Needless to say after about a year of trouble with the new kit the company decided to replace all the Huawei kit with Cisco 88x units.