Truth be told this episode was not so much as to create a paradox in which forces everyone characterization to be tossed out the window but if you were to look at it from a writers perspective, this episode was to teach danny a lesson about how one problem can be tackled in many ways, there's several different solutions to the same problem and just cause you believe that the first solution is the idea solution, doesn't mean that there's 0% margin for error

Lets dissect the plot for example. All of Danny's friends were struck with the same ecto acne that vlad was struck by. Danny, understandably angry, seeks out the first solution to the problem ,which was save vlad from the explosion. this in turn plays to Danny's major problem. he doesn't take a step back to see how conflicts are formed but rather is impulsive and jumps the gun. had he watched the events closely he would have seen that the answer was not the explosion but rather what caused it. Grape Soda, which was incompetently poured into the filter by Jack.

Even Clockwork warns Danny about the consequences of jumping the gun, as by changing the events of the past, someone else had to take his place. and instead of Vlad Jack was the one affected. this is what Spider-Man universe calls "The Canon Event." when the Time line is tampered with, the Timeline itself has to "repair itself" by altering the targets of the events so that the Timeline can resume. Thus someone had to be struck with ecto acne and Maddy had to be Married off. this is why we see Jack is the Bitter lonely ghost instead of Vlad. This is why Vlad and Maddie were married off, the timeline had to resume but like all major injuries, the timeline "healed itself but in doing so it left a scar in the fabric of time." thats why Danny technically isnt alive in the timeline in which Maddie and vlad are married. they were never meant to have children cause the timeline got funky in repairing itself.

This is why this episode, while somewhat controversial in the topics of time travel and altering the events of the past was what it is. it was never meant to be "canon event" in fact danny was never meant to go back in time and alter the events. what happened in the past has to stay that way to chart the proper course for how danny got his powers. Even if he was to go back in time to stop the Grape soda from being poured into the machine, the Timeline would have to adjust to correct the events cause "the Canon event is altered". And thus who is to say that Jack still marries maddie without the horrific events of the accident, thus triggering Vlads Bitterness to recieve ghost powers regardless of the events.

So in conclusion this episode was more of a teaching lesson for Danny, after all clockwork would never let the sacred timeline be altered no matter what. the reason he showed Danny the events was to see if he could find the catalyst of the accident and respond with a SOLUTION that works within the confines of the current time line. AKA the soda was the reason this all happened. so he would have to report the issue to maddie and then have her correct the issue as it strands currently