Not necessarily. If you're using a plenoptic camera purely for producing 2d images, you can reduce pixel size further than you would normally. This is because each pixel in the output image is the average of many primary pixels in the sensor. The primary pixels can be smaller and noisier while still getting a smooth output image. In rough terms the resolution loss is a cosine term over the pixel areas involved, so it's modest.

The technology also allows a tradeoff between resolution and sharpness that is novel, including the possibility of realizing resolutions beyond the diffraction limit.

The cameras used in research projects suffered reduced resolution because they were a frankenstein modification of an off the shelf DSLR. A camera designed to be plenoptic from the beginning has different constraints.

"color aberration and aliasing"

I believe these can be addressed in the processing stage. I don't see anything about either of these issues that's insurmountable.

"Low FPS. Each image requires lots of processing"

The processing can be done at any time after the fact. The primary image capture is just that, a raw image, same as any other camera.

The processing is also relatively simple convolution which can be done via FFT. Overall it's comparable to common video and image compression algorithms, not something new that requires a supercomputer in your camera.

"Proprietary toolchain"

There's no reason we can't standardize raw plenoptic images. Also, once the plenoptic raw has been processed it can be saved as any available 2d or 3d format, from png to psd to jpeg. These files will be fine in Photoshop or on the web.

"You can just produce a composite image that's sharp all over, but why not use a conventional camera with stopped-down[2] lens, then"

This allows depth of field independent of aperture size, which is a new capability. This will greatly aid low light photography, particularly dim landscapes.

But secondly, the images contain depth information, with all that implies. This is a very different tool from a stopped down lens. It's capable of realizing images that are physically imposible with a traditional lens and sensor.

"thrillingly expensive"

Citation needed. AFAIK each piece of technology involved is well understood and readily manufactured.