You can mix and match old and new. They specifically kept most of core 5e untouched because of compatibility.
No you can't mix and match. You have to go by what the DM/group is running. If the majority wants 2024 D&D because the mentality of "newest version of biggest brand name = best", then that's what you're forced to play. A new generation of kids are going to buy 2024 D&D and have ONLY that as their play material.
Does any game deserve to succeed?
Of course. In the same way that a great film deserves to succeed, but often doesn't bring the numbers financially, because it doesn't get the marketing it deserves. Hence trash like 2024 Twisters making tons of money, while Past Lives made very little, despite being something a lot of people would love if they were aware of it and felt the impetus to watch it.
It's not just a choice thing either. The dominant market force warps everything else around it, determines what can actually get funded. World of Warcraft was a mediocre, problematic MMORPG that continued to get worse over time, but its popularity caused investors to try and copy it, and the entire concept of what the genre was supposed to be fell by the wayside. But of course tons of people who experienced WoW as their first MMORPG hold it on super high regard, because that's what they know and it's what now impacts their nostalgia.
All information seems to indicate that most of us here have played more non-D&D TTRPGs than the designer of DC20 has
They've played RPG's their entire life and have a strong understanding of mechanics. Game design has a lot of overlap.
Oh, and as a side note, I looove McDonald's Big Macs. Love 'em. Like... A LOT. But I don't fool myself into thinking they're health food. It's a tasty, tasty treat.
So if that's an analogy the OP wants to run with, I'm down with it. Because.... Big Macs. Holy Heck. I want one Right NOW! I think I'll eat one while playing D&D online this evening.
And there is exactly the problem. A company like McDonalds is literally killing the planet (tldr; research the environmental impacts) and the health of society as a whole. Yet, like smoking before it, the majority of the populace regards it as "a tasty treat and nothing wrong with consuming it regularly". It's much worse than being a non-health-food. The way cows are raised these days literally causes diseases, not mention all the additives and processed crap involved in McDonalds that is seriously detrimental to people, but has simply being normalized by the toxic modern food system.