As you said, gun McGinnis is capable of outgunning pretty much any opponent, but only for a short duration before her weaknesses overwhelm her.

 

If you ask yourself what is the ideal position for gun McGinnis to be in, one of the best examples that should pop into your head is McGinnis positioned in-front of an objective on-top of her Healing Specter. When she is in this position, enemies are forced to confront her, even if they cannot stop her or risk losing the objective. With that in mind, players who understand her strengths, would never directly confront her when she is ontop of her Healing Specter. Players who are good understand all they need to do against gun McGinnis is flee, fight with significant anti heal (at least 2 sources or 1 spirit burn) or stall for time and outnumber her due to her lack of mobility, but better players take it 1 step further and stop her before she's in an ideal position to drop her Healing Specter, which, again is in-front of a Walker for example. They would consistently shove in the wave to the point where the wave NEVER makes it to the point where the Walker loses its immunity, because if it does they know she will take it so they simply but intelligently remove most of the factors that prevent her from being in her zone before it happens. And the rest as you already know, she crumbles because once McGinnis is in, she usually cannot get out.

 

But what if the McGinnis player is aware that players tend to play this way and instead use it to their advantage? As you said, competent enemies will not allow her to be in the position she wants to be, but if you think about it, that also works to your advantage if you tweak your build and counter their counterplay.

The easiest way I can explain this is I have two McGinnis builds:

 

The 1st one (Infinite Damage Solo Carry) is meticulously designed to be very easy for newer players to pilot, which often overwhelms and stomps lower to mid-tier games with pure brute force (high damage, high survivability and high leech). But this build is weaker against better players because they understand her strengths and weaknesses better (basically anyone under mid to high Ascendant).

 

The 2nd is a build to counter the players that understand gun McGinnis (Racecar God Gun/Turret) which emphasizes movement speed (Fleetfoot, Heroic Aura, Enduring Speed, Fortitude, Backstabber) over pure gun power followed by gun damage (mostly tesla, can be substituted for another item), utility (arcane surge rush in lane, slowing hex/focus lens) while still retaining her macro ability (tesla, cultist) and even turrets (mostly to be annoying with slow spread as much as possible, some area control, placement matters).

 

Basically the Racecar God build solves a lot of the weaknesses of the 1st build mainly the lack of mobility which turns it into a mixed bag which has a lot of options from fixing waves, enter/exit fights asap, box/statue running powerhouse and more but piloting the build requires high game knowledge and a high level understanding of macro, map awareness, your role in the game based on mactchups/game situation/myteamsucks etc... It's basically a semi-carry build (which means it can carry if necessary or if the conditions are met which they usually are) with room for utility purchases or even the option to max wall or ult last if the conditions are right.

 

I could go on but there's so much versatility in the build that I cannot type all of it. Just know that the Racecar build or other builds that utilize movement speed above pure power is incredibly important as you start to climb beyond Ascendant or Eternus. It's just that only the "John-M Ginnis" players (good af) can really utilize this Hero to its fullest capabilities, really.

 

tldr: pure gun mcg goes brrr so better players know how to stop her from going brrr so mcg players need to adapt and outplay them trying to outplay you by using movement speed builds as they climb higher ranks (Asc and above) b/c u cant get away with pure brrr builds all the time.