This struck such a chord. It is such, such hard work getting through those early days, and it is a very different experience to that that a lot of singleton parents will be having. I have an elder daughter too, who was a very chilled out baby, and her early months were a happy time of cafes with other new mums and long feeds in front of the TV. (I know that is very much not the case for all singleton parents, of course, but I do understand why you'd be looking at them and feeling like that!)
Then you have the additional emotional toll that IVF and the NICU will have taken and no time to process that. And the feeling that you should be grateful and enjoying it and enjoyment is very hard to come by. It's OK to feel like that, it really is.
And it will get easier.
As others have said, meeting other twin parents is hugely helpful, because they do tend to get it. And just get through this bit however you can (lean on people, lower your standards, work out with your partner what you both need and can contribute in terms of sleep and time off) in the knowledge that it will change. We refer to their early days as 'the haze' now, there is so much stuff from back then that I just can't remember.
About the 'magic bonding' guilt - I think this is totally normal with twins, and you don't need to read much on here to know that plenty of mums of single babies feel it too. I very much had the 'magic bonding' with my eldest, and I did feel the loss of it with the twins. The way I rationalised it was that they were part of a family unit in a way that the eldest hadn't been as a baby. There are pros and cons to all set-ups: only child, eldest child, twin, member of big family etc, and this was one of the cons. I felt particularly guilty as one twin was very demanding (colic, reflux, eventually diagnosed with asthma), and it felt as though the other spent the first six months of her life waiting in the bouncy chair. But they were part of a family that loved them and was doing their best, and I did my best to know that that was enough.
My twins are teens now, and having twins has overall been a brilliant experience that I feel hugely lucky to have had. There have been other challenges along the way of course, but nothing has come close to the difficulty of those early days yet. Keep on keeping on, you can do it.