While I'm neutral on masks, I think Labour's strategy to gain success now needs to be to focus on the hypocrisy of Johnson and other senior members of the government (e.g. Hancock). A pro-restriction line is unlikely to gain too much support now; I hope Keir Starmer realises this.
If you don't mind masks but do care about the rights of minorities then you probably shouldn't be neutral on masks - it's important not only to stand up for things that affect you. I only mention this because you curretnly seem to prefix every post with a note about how much you don't mind them.
Labour's response seems to be to not oppose the relaxation outright, but to suggest that the science should be made available so we all know it's a sensible course of action rather than an attempt by Boris to save his own skin. That seems like a reasonable line. If the government isn't even organised enough to cobble together some scientific support for their actions now, from a widely-fractured scientific and medical community, then they probably should all resign.
More prominently and importantly Starmer had a response that focused on doing relatively sensible non-disruptive things, many of which would help reduce disease spread and pandemic preparedness generally, like better ventilation in schools, better sick pay and UK sources of test kits etc.