Well okay some things. Coming from a person who has an AMD 8350, 6800K, Athlon II X4 630, Intel 4690k, Xeon 1230-V3, and a 4500U in the household and who had a 3570k. So no bias here. Just reporting my findings.
Yes the amd FX series is old at this point. Why do people still recommend them then? Because they are still competitive.
A) For gaming they are decent. They do well in a majority of games (maybe not as fast as an Intel in certain titles) but well across the board and they will even beat the i5s in a lot of titles. Especially at higher resolutions or running multiple GPUs. Plus streaming. The 8 cores kill the i5s in streaming. Sorry they do. My wife and I have the same GPUs in our rigs (Asus DCUII R9 290Xs) she has a 4690k and I have an 8350. In games the results are usually similar and the winner goes back and forth with maybe a 1-3 FPS difference. Only in poorly optimized titles like WoW and Day-Z does hers win. In streaming mine wins. Every time.
B) They do well in productivity. Rendering or in any application that can take advantage of the CMT architecture does well on the 8350. Which, from experience, is about the same as an i7. Rendering my 8350 is the same as my Xeon 1230-V3. The 4690k lags behind both of them.
C) They overclock well. The AMD FX series are great overclockers. My 8350 runs great at 5.0Ghz and will even hit 5.2 Ghz. Some people, enthusiasts, like pushing their hardware and enjoy overclocking so they are good choices.
D) The 990FX chipset is still a very good platform for most people. You get support for 1866Mhz RAM without an overclock with up to 32GB supported. A good number of PCIE X16 lanes (sorry PCIE 3.0 doesn't matter). All 6GB/s SATA 6. USB 3. Lots of USB 2.
It has everything you need and nothing you don't. Yes M.2 and Sata-Express would be nice but really IMO you don't need either of them.
E) Cost. AMD parts are cheap as hell. <$100 for the 6300. $100-150 for the 8 cores. That is cheap. Especially when they compete pretty closely with parts that are >$200. Better tech for the money? Not really. The 8 cores and particularly the 6300 can't really be touched from a performance perspective especially if you want to be able to OC later on. Really you'd need to go with the 4690k which is more expensive than the AMD and requires a more expensive (generally) motherboard. You can build two rigs that perform about the same. One Intel one AMD. The AMD rig will probably include an SSD and cost around $850. The Intel build will not have an SSD most likely and come in at closer to $1000.
Despite the two CPUs being similar in performance, most of the time CPU performance isn't even that important anyway. GPUs do most of the lifting these days. I'd much rather save money on the CPU and spend it on a better GPU or SSD.
Yes AMD is a little behind on their CPUs but I'd argue that is because they tried to innovate but the world wasn't ready. They bet big on CMT. That more smaller cores would be the way of the future. They lost.
Then they went to APUs and HSA. While this probably will be the way of the future software isn't ready yet so they lost there too.
Those two events put them behind Intel, whom, for a long time, was getting their ass kicked by AMD in terms of performance. AMD is coming out with new architectures soon. Zen and K12. Which should hopefully level things out again and push both companies to innovate.
Tbh I'd argue that the Intel parts are "old and outdated" now as well and that buying a Z97 motherboard for "future upgradeability" is stupid. The Haswell parts are not significantly faster than IVB or even SB. More efficient yes. But significantly faster? No. Buy Z97 for future upgradeability? Why? Broadwell will not be much faster than Haswell Just more efficient. So really no reason to upgrade from a gamers perspective. Skylake may see performance increases but that will be on a new socket so you'll need a new motherboard anyway.