With a product portfolio this big it is not surprising some parts are poor. Until anyone has looked with the same level of scrutiny at the competing companies it is not sure Huawei is the worst.
It's irrelevant if Huawei is the worse. What's relevant is Huawei's abismal incompetence.
Selection of vendors is a rigorous process in these multi billion deals. The products they are selling are extremely complex. They would not be winning these deals and billions of calls would not complete if they were as incompetent as your writing implies.
No different of a mess from firmware from any OEM or ODM's.
Just look at the recent Cisco user-agent "patch" for curl.