I've architected reliable systems on top of it but it was obvious to me almost from the get-go that Python is a terrible language. I credit my previous years of programming in Lisp that trained my mind to see through the Python mirage.
One issue is that veneer of Python user friendliness that lures people, usually those who are new to programming or don't have extensive experience with _multiple_ languages, in.
The major issue for me is that Python lacks internal consistency and is based on a inverted-design (meaning, no design really) that accumulated over the years and stinks. This makes it really easy for people to use Python and write unmaintenable code but also very hard for them to find out how to write good code. The hallmark of a terrible language is making good code hard to write.
As far as specifics, I think the module system is a joke, the packaging even worse, the REPL is not really a REPL (in the Lisp sense), ctypes is bad and has 100 different ways you can hang yourself with, there are tons of gotchas in the language and standard library that if you haven't memorized [usually by running into them], they will bite you hard, the GIL ties my hands, iterator/generator obsession makes for really bad code messes if people take it seriously and start poorly designing their APIs around it, absence of proper lexical scope, statements are not expressions and led to gross hacks like PEP 572... I could keep going for days.
Python is really the PHP of the 2010 generation.