I'd disagree slightly, I think it's one of the better multi-stage seats for using from newborn, although it's not as easy to get a good fit as it is in a well-designed infant carrier, it's not as simple as saying all infant carriers good, all multi stage seats bad.
Whether or not a good fit in the newborn stage is possible or important will also depend on several things; the angle of the seats and the isofix in your car, how big your newborn is likely to be (any idea?), how confident you are at fitting babies in car seats (totally normal for this to be 0/10, BTW) and how often you're likely to use the car within the first few weeks.
And whether or not it's better than an infant carrier totally depends on the infant carrier you're comparing with.
Newborns grow rapidly and it's common for a day-or-two old baby to fit terribly in all car seats, and for new parents to be so anxious about hurting their newborn that they fit the straps much too loose, but by 6 weeks most of them can get quite a good fit in the majority of car seats and parents have gained a bit more confidence too. You do have to be a bit more willing to get right in and manipulate the fit of the baby in the Joie i-Spin because the pads are so bulky they really get in the way, and you might want to consider likely weather, and how comfortable you will be standing in the car park trying to do this for the first time, perhaps with a screaming/uncomfortable baby, compared with a seat that you can take your time getting them into, then add blankets/sunshade as appropriate and then carry to the car.
The premium infant car seats are so expensive these days that I'm not surprised people are looking at multi stage seats from birth and for many people they can work well. It's about deciding whether you're likely to miss the convenience of being able to carry the baby around in their car seat or use it on a buggy etc.