This... this is GTA online. It's a cash cow designed to suck cash out of your pocket. Ads for things you can spend your money on are shown while "connecting", so if this delay wasn't introduced intentionally, it sure isn't a high priority fix. The code isn't part of the optimised, streamlined, interactive part of the game, it's part of the menu and loader system.
Most of these online games/services have so-called "whales" that contribute most if not all of the income the platform makes. If these whales are willing to spend the wads of cash they throw at the platform, they won't even care for another five minutes of ads. The amounts of cash some of these people spend is obscene; the millions Take Two profit from GTA every year are generally generated by only a tiny (usually a single number percentage) of the total player base.
In the end, I doubt they've lost much money on this. They might've even made some from the extra ads.
It's easy to forget that GTA5/GTA:O was originally a 360/PS3 game, getting a game of that scope running at all on a system with just 256MB of RAM and VRAM was an incredible achievement.
The A-Team developers who made that happen were probably moved over to Red Dead Redemption 2 though, with GTA5s long tail being handled by the B-Team.