[cranekam]

One thing I haven’t seen suggested elsewhere, at least from a quick scan through, is that you need to get more help from your boss. Your coworkers need to improve and your manager needs to help you with that by holding your coworkers accountable and dealing with them if they don’t improve. You can help define what “improve” looks like but without the authority to fire someone who doesn’t make it there’s no incentive to improve.

If your boss doesn’t want to help try talking to their boss, and so on. Presumably someone somewhere wants this business to succeed and can be convinced to care.

If that doesn’t work it might be time to find a new job.