Heavy losses are a welfare issue before they're a football issue. Players who lose 8-0 every week either stop coming to training or stop caring about the game. The coaching response needs to address both the football problem and the emotional environment simultaneously.
The short-term management
In the matches themselves: remove the scoreline. Literally — don't announce the score at half-time. Set individual performance targets that players can achieve regardless of the scoreline: "Your target today is to win 3 individual 1v1s." "Your target is to make 5 successful passes." These targets are achievable in an 8-0 loss and create genuine success experiences.
The structural fix
Contact your local FA or league organiser. Heavy consecutive losses at U9–U13 are a flag for league restructuring. Most leagues have mechanisms for moving teams between divisions — use them. Competitive balance is a welfare issue; asking for a league change is appropriate and expected.
The training focus
Train the individual technical skills that are the immediate cause of the goals: if it's defending 1v1 use the Wide Channel 1v1 drill; if it's possession loss use the Possession Rondo. Small, measurable improvements in training feed confidence in matches even when the score doesn't reflect them.
The conversation with parents
Be transparent. "We're in a tough season. The scores are difficult but the players are improving — here's what I'm seeing in training." Parents who understand the context and see the coach has a plan are far more supportive than parents left to draw their own conclusions from a string of heavy defeats.