That's pretty much irrelevant since the AMD's FX arch's issues weren't that SW at the time wasn't using all the 8 cores. Intel dropped the Core 2 Duo and Quad into the era where most SW was still stuck in single threaded for a long time and those CPUs still ripped single-threaded SW tasks regardless.

Here's the big reasons why the FX sucked back then and why they still suck today in the multi-thread SW era:

  Instead of discrete, fully independent cores, AMD grouped processing units into "Modules" where each module contained two integer execution units, but they had to share critical resources like one FPU, the instruction fetch/decode pipeline, and the L2 cache so when both "cores" inside a module were heavily taxed especially with math or physics-heavy calculations (like in videogames), they choked fighting over shared hardware.

  AMD designed Bulldozer with a very long pipeline, betting they could sacrifice efficiency per clock cycle in exchange for extraordinarily high clock speeds(a-la Intel Pentium 4) but the IPC was so bad that an FX core was often slower clock-for-clock than AMD’s previous-generation Phenom II chips and also their power consumption exploded. 

  FX processors were plagued by high cache latencies and an inefficient memory subsystem as another bottleneck.

Last year I picked up an e-wasted FX PC for nostalgia tinkering and boy, it definitely feels veeery slow today(just like Core 2 Duo/Quad), even on lightweight modern Linux(Debian 12.1) regardless of having as many cores as modern CPUs, the arch is just that bottlenecked, and when you add the missing modern instruction sets such as AVX2, FMA3 and SHA-NI, they only contribute to the slowness in modern use cases compared to today's CPUs that beat it while using much less power. It's fine as WindowsXP era PC for retro gaming I guess, but even then you can do much better with and Intel PC from the same era(i5-2500k for example) that's gonna be way less power hungry to boot. So unless you're into collecting pieces of history as display pieces, it definitely belongs in the e-waste pile instead of burning electricity.

It’s even difficult to find CPU benchmarks that don’t overemphasize 1080p and eSports scenarios.

My upgrade from 5600x3D to 9850x3D felt kind of dumb at the time, but I decided to do it because Micro Center’s bundle deals are so far below market pricing.

I was shocked at how much better it is. Benchmarks and FPS don’t really show things like micro stutters and little performance wrinkles like that. I’m not even sure 1% low FPS counts capture it.

A great example game for this is Oblivion Remastered. Upgrading my CPU alone with the same GPU took away the environment loading slowdown almost entirely.

The benchmark will tell you that I didn’t gain any FPS during gameplay but every time I open a door into the new environment my CPU is positively impacting the experience.

I would have said the exact same thing you are saying until I actually experienced upgrading to the best on the market. For the record, this is the first time in my life I’ve actually owned the best CPU on the market for gaming.

My old advice would have been to buy one of those sweet spot cheaper mid-range gaming CPUs, but my newer advice is really if you’ve already spent all that you’re willing to spend on a GPU (I have a 9070XT, my only upgrade paths are insanely expensive), buy the highest gaming CPU on the list for gaming benchmarks (e.g., I wouldn’t go crazy with a 9950X3D2 since it doesn’t have any gaming improvements above the 9850X3D).

And the thing about CPUs is they’re not insanely expensive like GPUs. We are talking a price delta of $200 between this beast of a CPU and something way more middling.