EDIT: Sorry for the long, meandering post ...
For me, I have been able to play old school style from 1e all the way into 4e though I found 4e to be very hard. It got progressively hard period so even 3e was harder than 2e which was harder than 1e. I didn't play 5e mostly because of mechanical objections not style but I suspect it may have gotten at least a little easier.
One aspect of my games is fear. So to the degree defeating the monsters is easy, I have to work harder to make sure it isn't so easy. Sometimes it's just not playing the monsters like idiots and other times it's having the monsters react after the PCs leave and return. I also like aspects of D&D monsters that have all disappeared because players apparently don't like those features. e.g. level drain, stat drain, etc... And while I've pondered it back and forth a good bit, I've kind of come around to liking gold for x.p.
As far as the game being challenging, I've been able to challenge groups of all levels in 5E and, to me, it's not particularly more difficult than it's ever been. It's certainly easier than some previous editions at higher levels. I do customize monsters now and then, more so at higher levels, but I've pretty much always done that.
But when it comes to things like insta-death, level drains and so on, that does come down to wanting a certain playstyle. Or maybe not ... you also mention XP for gold as an example, but what's the point of it? Is it just because you grew up with the rules and you remember having fun with a specific set of rules? Because that seems to be distinct from playstyle, that's a rule preference.
We almost always found ways to avoid level and stat drain, I've never played a game where we used gold for XP (I threw out XP sometime during 2E's run when I got back into DMing). We either ignored or created house rules to fit our preferred playstyle. Seems to me you can go the opposite way as well if it's what you and your group want, by adding house rules for all that back in. It doesn't seem like it would be particularly hard, just a note in your plans for the session. Then again customizing monsters is something I've always done.
One thing I don't see much when people describe their games is resource management fear. My wizards would never drop a spell on a pack of goblins the fighters can handle easily. Of course if it's an unlimited cantrip they would do that. I don't like unlimited magic. The fighters never felt useless or worthless in my campaigns. Thieves could use some work but I think I know what to do there.
Rules obviously can dictate or push a certain style, but back in the day before cantrips we just invented ways for the wizard to be effective throughout every fight. Maybe that was the 5 minute work day, more often it was scrolls, staves, wands. Because our style was to buck the rules a bit, we wanted people to feel like mighty damn heroes, not that wizard who cowers in the back because they cast their 2 spells for the day. As it is cantrips still feel like I'm throwing darts when the barbarian is doing at least twice the damage. But at least my wizard is doing magic "pew pew" while the warrior types are doing the energizer bunny hack and slash.
Being completely drained of resources that my character specialized in was never really a fun thing for any group I've played with, even if resource management pressure still plays a part. In other words, the rules that mean the wizard is down to cantrips, the barbarian is out of rages, the fighter has no more action surges, that type of resource drain better fits my preferred style. Before 5E? We just found workarounds. Same way that with the 2014 rules we house ruled in drinking potions as a bonus action and now it's officially part of the 2024 rules.
So that all goes back to playstyle vs mechanics. Mechanics obviously influences playstyle, but D&D has never been particularly rigid concerning playstyle in my experience. Many other systems go from one extreme to another. In some you know that you're going to be playing a group of thieves planning a heist with rules specific to recreating the feel of a cinematic experience. Because you've decided to let the game designer decide the style and theme of game they can provide rules for that. In other systems you have narrative games with very minimal rules. The former wouldn't be something I would want to play for a long campaign. For the latter when I've tried it, some people would build on other people's ideas but others would just ignore it and push for a different direction until everyone followed along.
I like D&D because it's fairly easy to tweak the rules to reinforce a specific playstyle while having a narrative structure as open as the group wants. We could all agree to play a linear campaign, the DM could set the stage and let the players do what they want, the players can help build the world, or anything in between. It's design is for longer term campaigns with a variety of challenges and opportunities
Whether the designers have hit the right balance with D&D is going to vary by individual and group. For me it has.
