I’ve been hearing a lot about how unreliable the F-35s have been with it being hard to even get them off the ground half the time due to the maintenance needed on them.

The F-35 requires roughly the same amount of mmh / fh as the Gripen, exclusive of engine and air-frame. What's been hampering the readiness rate of the F-35, which is below that of the Gripen, is the lack of maintenance depots. This was always going to happen because Lockheed planned from the beginning to sell the planes first and build the maintenance depots later. The F-35 sold so well that it outstripped the capacity to build the maintenance depots which created a lack of on-hand parts and technicians. This is turning around and readiness rates are improving as Lockheed slowly gets caught creating maintenance yards.

The Gripen has lower sales (that's not a knock on it) which made it easier for Saab to keep up on the maintenance side. They also try to get maintenance depots setup simultaneous with deliveries. IMO they've done a better job of managing things.

For comparison, the F-22's skin had a reputation for scratching from a rough touch and straight-up dissolving in spilled jet fuel (or even water). Stealth aircraft from before that were basically allowed to be usually-hangared money pits because they only needed to fly occasionally, to collect intel or end the world or whatever.

The process of designing the F-35 was insane, slow and cost billions and billions of dollars, but that's because the requirements given were over the top. They asked for three planes in one (an Osprey, an F-16 and a B-2), and eventually actually got something like that.

The other guy says they come out about the same as a Gripen, which would be remarkable because the Gripen is designed to be run out of a forest during a Russian invasion of Sweden, and not stealthy at all. Maybe it's more with the engine and air-frame. Either way, it's decent, and they like to brag about how almost all the parts can be reached without disassembly (they're "one-deep").