You asked what you could do as a solo player. Since you cannot fight a 4-man squad as a solo player that means that unless you manage to somehow instill teamwork into a random team not even speaking the same language it’s not going to happen.
Failing that try to fill the missing links - typically there’s no engineer (with active heals) on a random team, so bring one and be good with it and the balance of power shifts a lot - or pick a ship that allows you to influence the battle solo , e.g. a recon that can instantly get you to enemy beacons and quickly capture them while the enemy is busy camping your spawn.
This. Take these words into consideration carefully. A lot of players rush into battle solo (or even with squads), based on a principle “I need to level this ship up”, and they will fly that torpedo frigate or whatever else they need to level with no regard to the game mode, no regard to the battle situation and no regard to your own team and enemy team composition. And than they wonder why is it so hard, and why they just keep loosing. Try to start actually thinking for a change. Now, taking aside completely outmached games I am giving this advice for your general everyday solo, and how to improve even against a tough team, you can still make trouble for them. So, if you want to win, and not just level up your ship, you will have to start using your head a bit more and start thinking a bitt differently. Cool down and take your time. Observe what your team is doing, what are they bringing, what is the objective, what is the enemy doing, and figuring out where the weak spots are and how can you influence the course of the game as a solo player.
Let me share my experience. This reminded me exactly on the games I had in random 12v12 ESB lobbies. The game modes were Domination, and most of the players were from their corp, with a few other well known pilots from other major competitive corps, and since it was put to auto balance there was no time to even think about forming squads or using voice comms with majority of the players not even speaking English. So, it was mostly down to ourselves how we will adapt in these games trying to work with other random (but very good) players.
A lot of interesting games happened, also often seeing one side being completely disorganised and stomped by the other side (once one side starts losing and getting stuck on the respawn, this process can lead to an avalanche-like effect, that drags down a disorganised team even more).
So, after trying to support the team with the engineer, but seeing I receieved no help from the rest of the team because they couldn’t hear of notice I’m in trouble early enough, or notify me of their plans, this wasn’t working out perfectly, altough it was more helpful than using a fighter ship, which was an tasty target in game mostly full of interceptors and other fighter ships, and you could not do much by yourself planning that overdrive dive attack anyway.
So, after a few games, I noticed what both teams lack: focus on the objectives, therefore beacons. They were keen on dogfighting and and trying to seize control around a certain location, killing off as much ships as possible, often leaving side beacons open (altough not for long, the openings were still there and sometimes not exploited).
After noticing this issue I immediately decided that our team needs a recon, so I switched the role exclusively to that and started focusing on only one objective: fast capping early side beacons and backdooring anything else not protected. Often I encountered resistance but since i could hold my weight in most fights, I was lucky with the caps and managed to secure most of the objectives (that was also before the Recon nerf, and after these games it became my favorite role… until the nerf). Once I started doing this, our team has won every game. But as long as I was trying to do anything else in that particular situation, trying to beat the strong enemy killer pilots was like pushing with your head trough a brick wall, so I just went around it, and it worked. Every time. It gave our whole team that little edge, that little distraction that they needed to disorganize and spread around the enemy fleet.
I hope this gives some insight about how observing the situations in battle can help you chose proper role and your objective as a solo pilot; even against death squads you can still finds way to support your team as long as you have at least some kind of a decent team on your side as well, do not give up and blindly go into the fight; start thinking and looking what your team is doing and where you could help out - for the greater good of winning the battle by focusing on key objectives that will either break apart the enemy composition or become an imparable distraction or a blow to them, these are the ways that you can help, as long as you start thinking more open and looking at what everyone is doing, and find the gaps where you can possibly turn the tides of battle in your favor.