I couldn't resist contributing to this discussion, chat play was my only outlet for so long that I have become half addicted *grins and points at user title*

for clarity I will split real-time, text-only, play into 2 camps, role-play and cybering:

Role play is where I am not myself, maybe I am younger, maybe an abductee or rape victim, maybe a space captain or a victorian scullery maid... this is a LOT of fun, yes it is pretend, but so is pornography, erotica, fantasies....
Cybering is where I am horny / needy for something and someone else feels the same / wants to play... this is often more sexual because pleasure is easier to induce in words, to evoke, than physical pain is.. but the dynamic can be very real and very present without the requirement for pain, it can be in the smallest things, the 'keep your hands on your head'..the rough physicality of taking and forcing, the thing that just the thought of it makes you feel Dominant or submissive... a hand on the throat, being pulled about by your hair, or just being used and thrown aside....

The powerful reactions you can get to erotica that really hits your buttons? Like that, but interactive, you are writing a story with someone that addresses both of your precise desires and wants... it is not clinical as 'i put my tongue on your clit / I say ooh i like that', not is it usually as flowery as your examples, (i am sure I would be able to get permission from the other person / people involved to send you an excerpt or two if you wanted a more concrete example, but of course that would only show how the subset of people i play with, play)....
there is a connection, you are writing to turn on your partner, and you are describing the way your mind and body reacts to the things they are writing to try and turn you on, I have orgasmed from nothing more than rubbing against the bed a little during very intense play.... I think it is something that comes out of the desire being so strong that it finds an outlet, if rt is not possible / practical at that time (or even, for some, it is such an enjoyable process that they will do it in addition to having a full time rt relationship)... the fact of the matter is that after it both people (or 'all the people' depending on what you are doing) feel good, feel satiated to a degree.. there is often even an element of aftercare, especially in more intense play, where a skilled Dom can add predicaments, sophie's choices and a well described enough 'x' that you feel the pain or fear (as mentioned, a harder sell than pleasure)...
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Role play can also refer to longer-form (not real-time) types of play, see the role play forum on here, where it becomes even closer to a 'choose your own adventure' erotica..

i think it depends on your definition of meaningful - - i have had plenty of 'one night stands' for chatting, where I do get my sub itch scratched and I do feel so delicious afterwards... also I have some regular partners who it only takes a few lines before my breathing changes and i am squirming on my chair...
the saying about your brain being your biggest sex organ? It's so true and if you let your mind take the lead, let your body feel the pleasure, oh my goodness *does a very wide smile*
I would guess that if the best erotica you have ever read made you feel the sensations described, made your body ready itself for sex and made you feel awesome at the body shaking - wet sliding - pumping clenching worlds best cum... then maybe you will enjoy online play, especially if you have a creative bent and a desire to please.
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I like just_ine's definition of scening (online scening?) and either that alone.... do this for me, now press there, I want you to fuck yourself for me, i want you to spank your dirty fucking clit 'till you scream..... . Or to add potency to RP ....I want you to use a certain toy / do a certain thing towards the climax of the play... Is also very cool, but, for me, not as good as getting so mentally involved in something that I am there, I can taste, smell and feel, and, oh fuck can I feel *shivers happily*.... your body knows what it feels like to be touched there, and stroked here, penetrated here and slapped in the face.... and for a lot of people if you just let go you can feel it...

There is joy to be found there if you are wired that way... not everyone is. Because this forum is stuffed with readers and writers (it is, after all, a library) it is not surprising that it is a hotbed of getting each other off with words *grins*