it's almost a skill-less weapon as the only necessary information to use it effectively is the correct place to stand on every map and repetitively fling down into crucial areas.
As a Dynamo main I can tell you that's certainly not true.
We have to get a grasp on the very specific distances it takes to make sure we aren't in range of getting shot but we can still hit them, as well as the distance where our flicks will actually be effective since only hitting with a single glop only does 25 damage. We have to be careful on when we take our swings as well because a good opponent won't give us time to wind-up for a second if we miss, particularly because the way our flicks arc, it's easy to go right over the target's head. Bad Dynamos are pretty obvious and easy to kill once you know how the Dynamo operates.
Too many players have the mentality of go-go-go whenever they see an enemy, and usually die trying to rush us down. It's pretty easy to see a Dynamo because we hop before our long swing wind-up, which is something most other rollers don't do. It's really about baiting an exploitable response because of our high commitment. Hell, if we wind-up after you've thrown a grenade, we're finished.
If we have the advantage of height or surrounded by our own ink, that's not a Dynamo only advantage.
Any enemy who has the high ground is immediately at an advantage because they can hit you while you can't hit them as easily. Honestly, a good Charger or Splatling are far better at holding ground then we will ever be. I usually can't beat a good Splatling, close range or not, at best we trade.
I'd say our biggest weaknesses are Chargers (obviously), Splatlings (dat range), good Tentateks & Jr.s (if we miss, we die), Squelcher (surprise! unexpectedly out-ranged), but also the Krak-On has a very good means to counter us because it can cut through our ink and kills us during our wind-ups. Some of the most common weapons really.
Like any weapon we have our weaknesses, it just takes using a bit of patience, which is hard in a fast-paced game sometimes, especially for less experienced players. We don't auto-win, especially not in ranked, they dodge our initial shot and we're dead before we can wind a second.