re: Camera gurus, I need info please

No one is questioning the quality of the 5d4. It'll probably be my next camera body. No one is saying it can't make great images in auto mode either. I would hope that for $3500, it can take nice photos with reliable AF in auto mode .

All that said, you missed the point entirely. The t3i can make fine images in any mode, and telling someone brand new to photography (who is asking for lens advice) to rent a 5d4 - a professional camera body that takes substantial time to learn properly - just to shoot in auto mode, when they've already got a perfectly capable camera to suit their needs, is absolutely ridiculous. Particularly considering once their rental period is up, they're again left with nothing but a t3i and a 50mm prime. Not to mention, someone new to photography is likely to balk at both the $3500 purchase price of a 5d4 body alone, or the $300+ it would cost to rent a 5d4 plus something like a 24-70 2.8 for a week.

OP's s/o could get a used 18-135mm kit lens to keep and actually learn things for less than it would cost just to rent a 5d4 and an L lens for one week.

Again, no one is doubting the quality of the 5d4, nor is anyone doubting its ability to take incredible photos. That was just bad advice. A t3i with quality glass in skilled hands will produce better images 9 times out of 10 than a professional body like the 5d4 in the hands of a novice photographer. You don't need to spend thousands and thousands of dollars to make good images, and if you believe you do, you don't understand photography as well as you think.