This is a question I get asked quite often. My answer is always, does it really matter as long as I'm producing high quality images? Yes, you have to have decent kit to produce decent images but if I showed you two images from different cameras and two different lenses, would you be able to tell which came from what camera? I certainly couldn't and I'm a pro photographer.
Certain online bride magazines say "Choose your photographer only if they use Canon or Nikon and full format!" Full format? No such thing, they probably mean full frame but really haven't got a clue. Full frame is equivalent to what you got back in the days of 35mm film cameras.
There are of course, other different formats for film and digital cameras, from full frame, half frame, micro four thirds, large format, medium format etc., etc. Some photographers still use film and there's nothing wrong with that.
I'm one of the growing number of wedding photographers who use mirrorless cameras, lighter than their DSLR (Digital Single Lens Reflex) cameras. They're lighter because for one, there's no mirror box but they produce just as good quality images as a DSLR.
My preferred camera choice is Canon as that's what I cut my teeth on back in the later days of film cameras and early days of DSLR's. I tend to stick to professional grade lenses for obvious reasons as entry level lenses just aren't up to the job. For the main ceremony I'll have two Canon full frame mirrorless cameras and up to four professional grade lenses to hand.
With these, I can cover from very wide for those low sweeping shots of the venue to close up zoom without getting in your face so to speak and also something in between. I can also accommodate the larger group shots with the wide angle lens should the need arise.
For the individual portrait shots, I can use one of my long zoom lenses to really make the subject stand out from the background.
In my bag will be a couple of flashguns but I usually reserve those for the evening reception. My main lenses are more than capable of letting more light in thus eliminating the need for flash. Some Celebrants require that flash isn't used during the ceremony as it can be distracting, it can also spoil the ambience and the ambient light. My lenses all have Image Stabilisation so can shoot at much lower shutter speeds to let more light in, unlike your entry level lenses.
I will of course have other backup equipment, including two back up cameras, batteries, spare memory cards, etc. This is something else to consider when choosing your wedding photographer as you only get one chance to get it right. Like life itself, there is no rewind button.