I’m all for a challenge, I have no problem with that. I like games that are hard and make me think
This might not be as true as you think it is.
There’s nothing WRONG with that - lots of people don’t ACTUALLY like a challenging experience in their video games, they like a power fantasy or the illusion of challenge and that’s cool. It’s a game - we play for fun.
That being said, the Guardian challenge really shouldn’t be giving you THAT many problems. It’s been effectively nerfed extremely heavily since Shadowlands due to how much damage Bear as been given in their base toolkit and especially with Moonfire. But I can understand how it might feel a bit overwhelming if you’re coming into it from just world content or regular dungeons etc.
The thing is the Mage Tower challenges is that they are essentially a dance. They are HIGHLY scripted, and once you learn how they behave you’ll find you can do them forever. There’s a few things that you can do to make things easier on yourself though.
As people said, grab a Ravaged Seed Pod trinket from Emerald Nightmare. It’s easy to get, and any difficulty will work as long as it’s over Item Level 120 (so one you have in your bank from Legion won’t work, since that’ll be Item Level 50) - Also make sure that all your gear has enchants, gems etc. Easy to overlook but makes a big difference when you’re scaled down and need all the DPS you can get.
Try to let the adds get to the end of their cast (or at least halfway through if you have iffy internet) before using your incap. The VERY BEST way to do it is to actually let them JUST start casting. This is dangerous and you’ll want to make sure you’re not right on top of Velen when it happens, but it’ll prevent them from casting again for the longest possible time if I recall correctly (sorry, it’s been a while - I did most of the challenges recently but not Krull or Twins)
Another thing you can do is get the best consumables - getting the Scroll of Battle-Shout and Scroll of Fortitude will help, Boralus Blood Sausage in a great main stat food and Potion of Unbridled Fury is a really strong DPS potion. Obviously use Drums too, but save those for the second phase.
Get good at using Feral Charge quickly if you get distracted and knocked off by an eye - you can also quickly swap to Moonkin and use Feral Charge to yeet yourself back to the platform - this saved me on my kill because I lost concentration.
Still, I’d suggest you leave your ego at the door when it comes to the Mage Tower. It definitely shows you that you’re not as good as you think you are (unless you walk in and bowl it first try~) and it’s basically the only form of solo, truly challenging content that we have in the game. Getting my Book mount a few weeks ago was one of the biggest accomplishments I’ve ever achieved in this game and it felt great because I really felt like I earned it. You couldn’t just walk in and get it first time with good RNG like you can with lots of other mounts. These challenges are tough, but fair. None of them are impossible, and in fact all of them are doable on Level 60 Trial characters missing 10 talents, so a properly geared Level 70 with enchants and consumables definitely has the tools to succeed. The only barrier is your own ability 
Best of luck, I’m sure you’ll get it! I know people who have done well over 100 attempts to get their Felbear but they’ve said it was all worth it. And honestly, the destination barely (pun?) matters - it’s all in the journey. Enjoy.