Usually Monstera will have some root buds (for the development of aeriel roots) coming off of the bottoms of some of the stems. I would pick those segments to try to propagate. I have a "monster" monstera (excuse the pun) in a 35 gallon container that puts out tons of long roots from the stems. This plant is huge, its leaf stems are 5 ft long and leaves are the size of platters. It would be nothing to cut them and start them growing. SMaller plants, I don't know.

The leaves it does have appear to be healthy. They seem to naturally shed their lower leaves, especially when grown in lower sunlight. I've had mine growing outdoors all year long in very bright, indirect sunlight, and it still shed a couple of older leaves. But it grew several more to replace them. These "monsters" have no problem with growing roots. It looks like someone pruned away all of the aerial roots on that plant to make it appear "prettier." You can cut off the healthy tops with some of the stems and plant them. I repotted my Monstera this past spring and hacked away most of the potted roots because they were so rootbound. There was no hope of untangling them. I repotted my plant back into the same pot with fresh soil, and my monster just kept on growing as if nothing happened. Now it has sent out all new roots and filled the pot back up again, half a year later. Your plant seems fine, just a bit leggy. You shouldn't have any problems with cutting off the tops, with some of the stems, and planting them in their own pot. These plants are tough. They don't call them monsters for no reason, HaHa. :) You can probably even cut the bare, leggy stems up into smaller pieces and propagate new plants from those. Just make sure that they're oriented correctly, and not upside-down.

I would put it in a wide shallow pot..wind the roots and fit them in. Plant the stem sideways as I see you have two good sets of node roots. Way no,2 Is upright...but tuck in all long roots. Too bad the best set of roots are highest..but it will work. Should sprout in a few weeks. If its warm where you live then even faster.

probably not .. especially the mushy part ... but its hard to go further without a pic ... that said.. if it had roots ... you should have planted it.. rather than keep changing water ... again .. without pix.. perhaps you ought to cut off the mushy part .... let it dry overnight.. and plant it in the morning.. if you have any rooting compound with a fungicide in it.. it might help to dust the roots after they are dry ... and if you have others not affected.. separate them from the bad ones ... ken