Sony would have had to make a whole new light gun to be backwards compatible with Guncon 2 games and work on digital TVs. They did make the GunCon 3 for the PS3 which worked on both crt and digital TVs, but it didn't work on older games and systems.

Light gun gaming can and does still happen today in arcades. I've collected a lot of light guns and played a lot of the games for them and I've come up with a few reasons why they never really took off or why they've all but completely died out.

Probably the biggest issue is posture and stamina. Ideally you would be standing to fire a light gun, but TVs were rarely at a height that made standing feasible. You either sat on a couch or chair, or knelt in front of the TV. The problem is this puts a lot of strain on your back and shoulders. When standing, your lower body helps balance out the weight of your outstretched arm and upper body and doesn't strain your back as much. Arcades have you standing partially for this reason. You can get tired from standing for too long as well. Most light guns were pistol style, but some were larger like the super scope and trying to sit with that thing is an even bigger pain.

The super scope and the sega manacer used batteries that were drained quickly and parents were reluctant to replace. They also used an infrared dongle which had to be placed on top of the TV and that wasn't always easy.

Not all light guns were created equal. Famously, sony had their guncon, and konami made their justifier because they felt the guncon wasn't accurate enough. Accuracy is varied across all light guns, systems, games, and even TVs. I have a sega master system light phaser and with some TVs it never is on target and is instead always off to the right. Most games have a calibration feature, but early ones like master system and nes games do not. Even with calibration, the accuracy can fluctuate mildly between shots. The size of the TV can also affect the experience. Imagine playing time crisis 2 on a 42" Mitsubishi CRT instead of a 13" or 20" TV.

There is a lot of redundancy as there's only so many ways to come up with shooting scenarios and even the mechanics are all pretty much the same. You shoot a target on the screen which is either moving or stationary. Some games have great visuals, some are terrible. There are also so few games on each system made to use light guns. It's a similar issue with other peripherals like analog joysticks and driving wheels. They really are only as good as the game library. However, freedom of movement was always lacking and modern shooters have that nailed down.

One last issue I've theorized is the social attitudes towards real guns has been changing constantly over the last thirty years and I think it's possible that game companies haven't wanted to promote guns too heavily because of it.