I disagree with the conclusions of this article, and feel that the author didn't provide nearly enough evidence to back up a pretty big claim. The notion that the F-35 is a high-end and expensive asset is not some new admission, nor does it mean it is a failure. While it was meant to be a lower-end plain initially, it hasn't been considered that way in a long time. And while I agree that the F-35 is expensive and we may need to supplement it with a lower-end fighter, that's hardly a failure. That's exactly why we ended up developing the F-16: because we needed a lower-end fighter to supplement the F-15.
There's plenty to criticize about the F-35, particularly about the procurement strategy and development cycle. But we are starting to see real results. The F-35 has performed very well in exercises like Red Flag. And I don't think you can understate the importance of the F-35B. Yes, it has markedly worse availability rates and maintenance issues than the other variants, but that's pretty common for STOVL aircraft, like the Harrier it is replacing. And not only is the F-35B the only stealth STOVL, it's also the first production STOVL aircraft capable of supersonic speed.
I also think it's weird to imply the reason the F-35 has failed (and I don't belive it has) because it's been made in three different variants. That really isn't the reason for all of these delays. There are several examples of aircraft being able to work in multiple roles, like the F-4 and the French Rafale. The fundamental issue is in avionics and logistics. All of these sensors and systems are very complex and difficult to integrate together. Any aircraft with a modern, full-featured AESA radar and IRST sensors sees a protracted development time.
In terms of purchasing new, lower-end aircraft, I do think that's a good idea. Depending on where you want that to fit in in terms of doctrine, you've got a couple of options. The USAF is already starting to purchase some F-15EX planes. It's got decent range, good performance in air-to-air and air-to-ground engagements, and it's based on a mature platform which should reduce costs and improve availability. But it's a fairly big beast, and operational costs will still be higher than legacy F-16s. The other option is to go with a genuine light fighter like the JAS-39 Gripen. Cheaper, much lower operational costs, and capable of operating from short, rudimentary runways, but shorter range and less payload capacity. I also think there's space for a "featherweight" plane, like the A-29. When we're engaging Taliban targets that don't have anti-aircraft defenses beyond small arms fire, a simple turboprop will get the job done efficiently and cheaply, and that frees up jets to be used in other theaters.