E-cores are necessary for Intel to compete with AMD on multicore performance. The problem is there's also a ton of workloads that don't scale well with cores so you also need P-cores. If Intel was only interested in pure multicore CPUs then they'd probably go E-core all the way as they achieve much better results than P-cores both in terms of performance/W as performance/die. Most people don't seem to understand the Big.little approach and why it exists. The idea that marketing determines hardware and not the other way around is laughable. Of course for gaming E-cores are mostly worthless.
Atleast from the leaks it seems like a succesful approach. Intel increased multicore performance by 60-70% in a single generation. I doubt they could've reached 5950x MC performance wihout E-cores. There's no way 2 P-cores would outperform 8 E-cores. Most likely AMD will do the same thing in the future as it's the most efficient way to increase multicore performance. AMD can just delay it because their cores are much better in terms of performance/W than Intel's cores.
Compete with AMD on multicore performance.... where? For what market segment or use case? Server?
For the MSDT stack, 8 physical cores was already enough, maybe 10-12. Intel has them. They perform just fine, albeit at high TDP. As someone else stated, you do get more cores for the same TDP at AMD, and its also high. But really, the market for Ryzen 9 on MSDT? This is not where Intel gets the revenue.
You said it right. There is no E-core use case for gaming. So let's summarize the real world advantage for Intel here.
- The vast majority of MSDT-aimed use cases don't have any advantage.
- The core count on Intel products apparently goes up.
- The larger half of the ADL stack doesn't even use E cores.
- ONLY the SKUs that have E cores on desktop, benefit from a marginally lower idle usage and Intel can divert some margin of power headroom to the P core. Benchmark win. Yay. Real world use case? There is none. If you truly have a heavy multicore load you'd also need instructions to go with it. And if its simpler but still parallel, the thread count matters as much as frequency. So maybe you can transcode something a little bit quicker, by virtue of a double core count

Worth...
- Any basic home PC doesn't even remotely know or care about all these developments and is fine with a 5 year older CPU, 2015 quad core would do the trick fine even. And here's the kicker... those already had 65W TDP too and idled well.
- On mobile, the same use cases exist, minus the heaviest desktop ones. Added use of more E cores alongside P cores? I don't see it, apart from, again, marginal power usage advantages. But laptops barely even idle more than desktops, if at all, because they just hibernate.
The competition here happens on IPC and mostly on benchmarks. The benefit of E cores is pure marketing: core count wars and synthetic wins. Its a bit like an engine that can rev in the red to show super high RPM, but it really can't drive continuously like that. And in that sense, its just Intel cranking out even more bursty CPUs for consumer, what's new? The real victory long term isn't big little. Its IPC increases, as it always has been, because the single core perf is pivotal for everything else. Not the way cores are set up, or split up... AMD has experienced a page of that black history too with FX.
Sure, its nice to believe in the idea that Intel is 'back' and 'competition is really on now', but I strongly doubt Intel has a design win here with the big little concept on x86. They can eek out a few % but the biggest win is the marketing win, much like the Megapixel, the Ghz, the Watts and all those other numbers Joe Simple won't understand, but higher is better. All I see is more CPUs nobody really needs, and exaggerated price points to go with it.