Yeah there's a million games like this you can't carry. And the worst is getting them in massive streaks. Like say 7 games in a row over the course of a week or so. The best you can do is try to feel things out. Like... is my team able and (more importantly) smart enough to ward up and stall at tower 4v4 or do I need to group/flank?
Before you decide to split or group - in addition to "can my team 4v4 stall/push w/o getting aced before I can join and save them" - you also have to consider:
map pressure (do they have it, do I have it, where to apply it, can you apply it in time, etc.)
minion wave locations and sizes (am I wasting time running here, should I hard push or slow push or freeze, do I set up a push and look to rotate/group or do I stay with the pushing wave)
vision (do I know where the enemy team is, can I infer it based on objectives available minion waves and other things, if they have so and so here can I beat them and keep pushing, where do I ward to prevent them collapsing on me without my team being able to punish, should I base and group or hide to make them think I left but actually stay, etc.)
objectives (towers, baron, dragon, buffs) (what's up right now or in the next minute, is it vital, can we trade it away for something else if we are behind and how do I set that up, can we force them to fight us for it if we are ahead, can we sneak one objective while they do another, what's more valuable, etc.)
Never an easy call. There will always be people who don't like the decision you make and harass you for it. Sometimes they are right and you should have known better. Sometimes they are right but you couldn't have known. Sometimes they are wrong and just mad, so they try to make you a scapegoat. And sometimes they are legitimately boosted 2 tiers above where they should be and literally don't have the brains to realize you made the right call and they messed up. In their shallow mind, they think they did the right thing and you suck. I try to give evidence backing up my calls, but it's not good to spend forever arguing. For example - a common problem is people who can't win a potential fight overextending and getting caught out. Whether solo, duo, or 5 man. If you can't beat the opponents who are there, you shouldn't start a fight with them. Moreover, you shouldn't position within their engage range or even close to it. Stay back by a tower and cede ground as needed. In such a scenario (with me splitting), I generally not only ping danger on top of the person, but also highlight the lack of wards they have to be pushed out so far. If the person is not a boosted "monkey" or intentionally feeding, they back off. Sometimes they don't listen though and there's nothing you can do about it.
That said, just because you CAN split-push and just because you CAN win 1v1 or even 1v2, it doesn't always make it the right call. Sometimes you are better off grouping because otherwise your team just melts too fast and they NEED you to frontline for them. Sometimes, you have to ruin a potentially perfect or amazing kda game to die every teamfight so that your TEAM can win the fight despite your carries having fed their butts off in lane. If the team will listen to good calls, stop making horrible decisions, and has the potential to win or go even in teamfights despite many members being behind, I will group for strategic defenses and to contest key objectives. I don't mind dying for my team if they are going to start playing properly and make good decisions. Everyone has a bad game here and there. When I see them making or listening to good calls and playing smart, I know they are trying and just had a bad laning phase; not inting or boosted despite the fact they fed.
Like I said with our bot duo here - sure they fed their butts off - but they also listened to sej and me and grouped to stall at key objectives (like mid tier 2 tower) - rather than continue to do their own thing and keep feeding (like decide they need to solo farm and push bot tier 1 tower for 20 min at cost of our base and at cost of dying to anyone on enemy team who goes bot to fight them). I've seen both, and had both legitimately think they were correct. The ones who solo ff lane just kept feeding, not getting any objectives, and cost the rest of the team any advantages they had, and ultimately threw the game trying to solo farm their way back into it. When you are lucky though, you get the bot duo like this one and they listen, group, win fights that shouldn't be possible to win because they trust their team, and they get back in the game via teamfights and then safely farming or pushing objectives when the enemy cannot send 1 person down to just assassinate them and stop them getting anything.
Same goes for toplaners or mids - even if they are fed like I was to start the game. I can't just blindly push my lane because I win a 1v1 and some 1v2's. I need to respect vision, map pressure, objectives and everything else. If I give their team a chance to 3v1 me, I can only put myself in that position if my team is set to 4v2 push some other equally or more valuable objective. And even then, I don't force a 1v3 - I just take the risk that it COULD happen in order to set my team up for success. If I die there 1v3, I don't complain because my team comes out ahead. If I die because I blindly or knowingly die 1v3 when my team isn't set to force another objective elsewhere, it's probably my fault. The only way it isn't is if my team was set to do so, but chickened out despite being 4v2.
Anyways, sorry for the tldr. Good luck learning toplane - there's a lot of diversity in terms of champ roles and stuff. You don't always have to play meta either despite what some will say. And if you want to learn some good basics that are applicable to any role, check out one of my favorite streamers - SoloRenektonOnly.
