Basically, if you aren't there at the start of the game, don't try to load back in. Just let your team re-make. You're putting your team at a disadvantage at the start of the game by letting your opponent have free farm and go to other lanes. If you're the jungler, you're letting the enemy have free access to your jungle and you're gonna get invaded a lot. The laners won't leash you, and if they do, they'll be behind. If you're the ADC or support, you just made your ally have to 1v2 miserably and be irrelevant for the next 15 minutes if nobody capitalized on it, in which case it just went up to like half an hour.
If it's anything past 1:30 and you aren't in the game, for whatever reason, please just leave it be. Even if it's "not your fault" because of your internet or computer. This is assuming you come back, which best case scenario, you're better than your MMR lets on and you can overcome the difference. A lot of times I've noticed is that if your internet is so bad you can't connect to begin with, if you manage to come back, you're likely just gonna DC again