Hello and Welcome!
I cannot pull your pictures up to magnify them so I will do my best.
Phalaenopsis is commonly though of as an "easy" orchid. However, it is difficult to grow and flourish under normal home conditions.
This is primarily because a humidity of 80% is optimal and well, if you're human, 80% humidity is hell
With lower/normal home humidity, roots can go through dry/wet cycles and eventually rot. Although cattleyas can tolerate this pretty well, phals do not. Thus your leaves wither and fall off due to lack of nutrition and water no matter how much you give them due to "no roots".
The rot can extend upward and is the same as crown rot but in reverse.
Other causes of root rot are just flat out overwatering. But I believe the previous reason is more common. If your potting mix is deteriorated however, it could be holding too much moisture and rot the roots.
Lack of light can be a reason why an orchid doesn't bloom but it would not be a common reason it deteriorates.
Leaving water on the leaves or in the the crown can cause a "crown rot" which goes from the top of the plant down...the reverse of what you have.
Temperatures that are too cool can also kill a phalaenopsis but it sounds like this is unlikely for your case.
So ultimately, I would conclude your root system is gone.
How to fix it?
First, cut your spent spikes down to about 1 inch.
Second, remove the plant from the pot and see how the roots look. Cut off any black or brown, soft, squishy roots. Save the firm white and green roots.
Third, repot with fresh orchid bark mix. You may need a wooden spike to support the plant if you don't have many roots left. Be sure the pot is as small/tight as possible.
Four, keep the plant a bit on the dry side with humidity tray underneath and hope for the best...
IF there are no roots, you can try "sphag in a bag" but for me...that's when I go to the garbage with it and buy a new plant