These aren't exactly loopholes. But I agree with you that most of this behavior should be punished under the current rules. But there's a difference between a loophole and how the staff chooses to enforce the rules.
"Get Good", "Rekt", "eZ"
It's nothing new that the staff doesn't usually punish or warn players for saying these words occasionally. There have been discussions about this
before. That doesn't mean the staff can't punish players for this behavior when it gets out of hand. In fact, under certain circumstances this is punishable with a kick or even a ban. As the rules say: "Do not antagonize other members or staff members in order to evoke any specific reaction to the point of including up to abusive reactions." And staff members do punish and warn players if needed. See what these moderators have to say about it.
DDoSing and DoSing
I don't exactly know where you're going with this. DDoSing is punishable. And it is punished harshly. But, of course, there needs to be proof. This is not a loophole or even a matter of enforcement. It's a question of whether or not there's enough evidence. And that's a practical matter that needs to be decided on a case by case basis.
Harassment is a permanent ban
How did you come to this conclusion? The rules only say "you may risk being permanently removed". It doesn't say this is always necessary.
"Spreading rumors is not allowed"
Are you saying this isn't being enforced? I'm pretty sure this behavior can be classified as abuse in certain circumstances.
"Stalking a player around the servers and constantly targeting them is considered harassment"
This behavior is also punishable. But you're referring to a specific case involving a streamer. I don't think this is the right place to discuss individual cases. About the enforcement of this rule in general in case of streamers I will say that I believe that streamers assume the risk of being targeted by streaming. They also have the benefit of fans following them around and teaming with them or receiving items from them. It's just part of being a streamer. I'm not saying that streamers have no rights when it comes to being targeted, but there should be a very high threshold before players get punished for following and targeting a streamer. Also, an easy solution would be to set a delay of a few minutes so the streamer can't be followed in-game by the players watching their stream.
"Keep the chat PG"
The swear filter isn't designed to catch everything. That's why we have staff members. And they do take slang into account. And with a staff as diverse as ours, they even take into account slang in foreign languages. I know many examples from my time as a staff member and I have personally punished players for using offensive Dutch slang.
TL;DR
A lot of the points you bring up aren't loopholes. The rules are not absolutely precise. Nor should they be. They need to avoid excessive rigidity and to keep pace with changing circumstances. This inevitably means that they are couched in terms which, to a greater or lesser extent, are vague. It all comes down to the interpretation and application of the rules by the staff, what they choose to enforce and how they choose to enforce them.
In the thread title you write "Not being taken seriously enough?". I can assure you that the staff takes every offense (whether it be reported in an abuse report, poke on ts or witnessed by a staff member in-game) very seriously. But keep in mind that all decisions are made on a case by case basis. One decision by a staff member you don't agree with doesn't mean the rule itself isn't effective.