What you’re facing is frustrating and I can’t fix that part. But I think you’re thinking about it a slightly-wrong way and if you change your perspective a little it’s easier to deal with.
The goal, for now, is not “get all mythics, any mythics, at all costs”. There are more than 40 mythics, but only about 6 of them are part of a meta team that is “needed” for very high level play. And speaking honestly, the most dangerous PvP team I use and the GW teams I lose most consistently to are made up of Legendaries.
So here’s a thought: until you have a surplus of resources, stop thinking you have to to get the new mythic every month. Some month, a new “as bad as Gargantaur” is going to come out. Do you think you should throw away EVERYTHING to get a troop you might never use? Probably not. Skip it.
But also look at a “decent” mythic like Champion of Anu. In endgame, I use it sometimes in GW, but not all the time. It probably won’t hurt you to miss a mythic like this and hope that luck or diamonds bless you with it later.
The reason you do this is because if 1 month of resources only gives you about a 50% chance, 2 months will probably give you 75, and so on. Eventually you’ll have an 80% or 90% chance of getting the new mythic. If you save up and only spend when the mythic is really good, you only fall behind “as a collector”, not “in terms of competition”.
Use diamonds wisely and start with the strongest mythics that will dramatically boost your capabilities. EliteMasterEric maintains one here. Ignore that it says it’s 4.2.5, he’s probably updating it and it’s not THAT out of date. Get the S-Rank mythics. Then the A-Rank mythics. Then, you can sort of stop caring.
It’s much faster if you’re an an active guild that finishes all of its tasks and gets all of its reward portals. The game’s economy assumes you will do that. There are plenty of these that don’t mind taking in players who “don’t have enough”. If you don’t want to join one of these, that is what is actually making you angry about GoW. (I think it’s valid to say the game makes being in a good guild too advantageous.)