Sadly when it comes to systems questions like these, what ever the designers intent the min/maker will always min/max whatever the new system limits are. The people that end up suffer are those who don’t know systems newbies
You may be right about SR, as its hard for me to think of a variant to the rules that would be sufficiently shadowrunny to make fans of the system like it, yet effectively deal with minimaxing. Having said that, there are certainly other systems that effectively address minimaxing and allow for design of several-dimensional PCs that are still 'as good as can be' at combat.
As a simple, partial example, SR 5's karma vs. chargen point difference is part of what creates such a significant drive towards 'tall stack' builds. This in turn encourages more one-dimensional PCs and stovepipes them into specific team roles. Games where experience and chargen points are essentially the same don't have that 'push' on the players. Sure you still want high pools, but without that, improving ones' skills in important secondary ways like sneak or con or perception at least aren't
bad point allocation choices. Different example: limits were
an attempt to deal with players maxing one or two dice pools at any cost, though IMO it mostly failed at that.
10 gangers will probably be a major threat in 6. Where they would be warm up in 5. Guns maybe less powerful but is almost nonexistent. 6e will be radically different and not to benefit of the players.
IIRC, in 6 you can target multiple people with a single burst or auto attack, which might make up some for dropping high init characters from 3-4 attacks down to 2. But I doubt very much any game system - including SR 6 - can stop GMs and play groups from picking whether the bad guys consist of "many tissue thin grunts lead by a few tough hombres" or "NPCs mostly built like PCs". Or even switching between those two models. It's certainly the case that a GM in SR5 could make a group of 10 gangers be tough to beat. The "challenge per enemy" or per enemy group has always been something the GM can control in order to move the game along or make combat more high tension...depending on what the play group thinks is most fun. "The benefit to the players" is not whether 1 NPC or 10 is a real threat; the benefit is what the players find to be fun - which can sometimes be 1, or 10, or 100, depending on the player, the group, heck it can even change from scene to scene.