Challanging combat and roleplaying are not mutually exclusive in all systems. HERO system is one that combines them well because talking is free all the time, and it is in genre for Super Heroes to trade witty banter, make difficult decisions, and fight all at the same time.
In shadowrun, combat is designed (from both a mechanical and genre perspective) to be short, brutal, and solved with overwhelming violence from one side or the other. You cannot have a back and forth shadowrun combat, where the outcome is in doubt. This is due to the offensive and alpha-strike nature of the combat engine.
Role-playing is more about the story and the fluff than game mechanics.
Even if I agreed with you (I feel the statement is too general to agree with in totality), It is not unreasonable to expect good mechanics. A group of children playing make believe can have awesome stories (see Axe Cop), but what separates them from RPG players is mechanics.
Onion Man played a channeling voodoo mage (one of the most high powered combat archtypes in the game), and thus was not challenged by anything. That’s understandable. That’s not the GM’s fault, but the Missions system for not helping all characters to be in a similar power bracket (12 Hardened armor > 12 armor for example). This problem has been hotfixed by banning future possession mages.
A bigger issue is vast discrepancy of 400BP, 0 karma characters. You can build 2 characters who are both “faces” but one may throw 20 dice at everything, and the other throw 17. The 17 dice face then becomes an assistant to the 20 dice face all the time. With 2 hackers it is even worse, as the other hacker just increases the chance for an alarm to be triggered. When you add in how bad the sample characters are, there is a huge difference between 8 built characters and 8 sample characters. This large imbalance is what makes building shadowrun missions very hard. There is no simple solution and gradual improvement is necessary. Don’t blame the player for playing a character that might have been acceptable at his home table, and legal in missions without realizing how overpowered it would be at missions.