DevOps is still a great idea, just like Lean and Agile are a great idea. But a great idea isn't enough. A million people have "great ideas" for businesses all the time. How many of those succeed? You can't just have a great idea, you have to execute really well on the great idea.
Most people don't know what DevOps is. Of the very very few that do know what it is, they are powerless to get other people onboard with the idea, because people are lazy and don't want to learn things or change how they work. Even if DevOps is great, if the executives in your company don't force it down everyone's throat with business policies, training, etc, nobody will ever actually do it, because nobody really wants to.
Platform engineering is not gonna solve what DevOps is failing to solve. It's just another silo. "Let's empower developers" sounds great. But developers still lack most of the knowledge to maintain a complex system. Give them a million super-powered tools and they will still screw things up. Most developers I meet today don't even understand the concept of DNS. That's not exaggeration - they literally don't understand how hostnames work, record types, zone delegation, authoritative records, ttls, much less propagation or transfers. And you want to, what, give them a fancy tool to change the system that they don't understand? You still need operations, in any business, not just tech. Somebody has to be paid to care about the boring shit that keeps the business working. There is no way to automate away that responsibility, in any complex system in the world. A platform eng team is just adding another team on top of the Ops team you will always need.
What would actually solve a lot of this - and nobody is going to like this - is boring-ass business management best practice from the 50s. W.E. Deming. Lean. Six Sigma. The stupid shit that MBAs nerd out over? That stuff works. High-performing businesses that don't just pay it lip service, but actually do PDSA, actually train their workforce, actually continuously improve their process, and make better business outcomes. But who among the tech nerds wants to listen to that? They just want to play with their toys and have no responsibility. "Build me a platform so I don't have to use my brain."
People have been studying businesses for the better part of a century. There is no easy way out of the morass. No single team or tool or paradigm will make things better. Until you consider everything, holistically, and put into place a barrage of different solutions, and actually teach people to do their jobs better, the actual outcomes of the work won't improve.