TR4 gives you a better platform. Better in terms of more RAM bandwidth, more PCIE lanes, etc. Does the avg user need this? No. I would argue that for 99.9 percent of users the TR4 8 core is a worthless product, other than the upgrade path to 16 cores that it leaves open. It's really pointless for most people. I don't think the 8 core TR4 CPU should even exist.
The average user has one M.2 SSD, 1 GPU, couple of hard drives, and for these people Ryzen 1700 overclocked for WAY less money is the right choice.
Ooh btw the TR4 CPUs come in a wayy cooool box. If that matters to you.
The 8 core should totally exist, I’ve built myself a nice games system built around that, no need for more cores yet, for me at least, it comes with the highest clocks of any Ryzen part (standard all core with good cooling is at least 3.9Ghz, zips up to 4.2 with XFR on 4 threads, many 1700s struggle to do 3.9) along with an extensive array of options to keep me going for a few years, I’ve already ditched hard drives for SSDs, I will be buying nothing but NVMe going forward, I already have one, it’s 4x lanes per drive, they are only going to get cheaper too, where do you go with the other boards, they all seem a bit dead in the water to me.
I think about the progress of my last system, it started quite modest with 1 GPU, but with time and screen upgrades etc I started to add in GPUs, drives etc, it could cope as it had all the appropriate switching for PCIe lanes via its PLX chip, x370 boards have less ability than my old z77 from 2013, x399 has it all.