I kind of hate to break it to you Celtavian but that's basically still the case, in fact, it's even worse now due to "bounded accuracy". Seen a level 14 Paladin solo a CR18 Dragon yet? I have. Thanks Magic Items. Oh did I mention I am handing them out at 1/4 the recommended rate in the DMG?
The only difference is now it's way easier to mess it up because the designers left it up to us instead of giving us some sort of reference point to work with. Even the rarity groupings are pretty poorly thought out.
And unless you actually plan on running a no magic items campaign, it's even harder now to design encounters with magic items in mind, because they're not assumed as part of the maths. Your players will still probably badger you now if they badgered you before for crafting, because the rules are still there, you do realise that right? And if you have oodles of downtime and piles of gold in your campaign, there's nothing really stopping them from doing exactly the same thing. If you couldn't say "No" to your players before, you can't say "No" now either, it's not really a rules issue, it's a DM issue.
Just like I wouldn't let you do ridiculous Simulacrum/Wish shenanigans, I'm not going to let you craft whatever you want, no matter what the book says.
And just so you know, most MMO's don't just let players craft whatever they want. They usually have a system which requires a lot of work and effort to get the rarest materials - usually questing and killing some sort of challenging boss. You can't just handwave it and then *poof* you have a legendary item, you have to work for it.
It would have been nice of the designers to actually put some thought into that area after the lessons learned in 3e, but nope, this edition seems to all be about "If it's hard to get right we won't even bother!"
I guess if I was bad at math it would be a problem. I'm not. I can usually add up hit probability, DPR, probably of magic affecting the creature including the relative benefits of advantage easily. The math in this game is quite easy.
I'm having an easier time designing encounters. Most likely because I had good training memorizing all the math in 3E/Pathfinder for multiple characters including commonly used buffs and designing ACs for appropriately challenging encounters. If I wanted a say "deadly encounter" in 3E, I knew how to make that happen during encounter design.
5E encounter design is the easiest I've ever seen. Are you really having trouble?
I've played both Everquest and World of Warcraft to high end raid level with maxed out all crafting skills. My friend models his quests off MMORPGs with more story flavor. It's easy to do.
Unbelievable that anyone is having trouble coming up with interesting ways to supply magic items. It doesn't take that much work. You don't need a price list. Just come up with something for a handful of magic items. The most each player can have is three attuned items. How hard is it to come up with some process for three attuned items?
If you're letting 14th level paladins solo CR 18 dragons, that's on you. I've had zero trouble designing appropriately tough encounters. Didn't you say you were making custom monsters? Shouldn't be very hard to make appropriately tough creatures for the magic item level you want.
Seriously, the math in this game is cake compared to previous editions. I hope most aren't having problems with the math in 5E.