As teams get bigger, finding unanimous consensus gets harder. Exponentially harder.
What worked for a team of two people, where finding full consensus in decision making comes easy, won't work as the team becomes bigger. Each new person brings in another opportunity for an opposing viewpoint, and a new opportunity to fail in finding a consensus.
Getting those extra opinions can be valuable but it can come at a cost of slower decision making, or might even result in no decisions getting made at all. Debate is healthy, but at some point you need to conclude the debate, make a decision and move on. If you require unanimous consensus each time, each decision will start to feel heavier, slower and more costly.
When a decision is to be made, there is a comfort in seeking full consensus. If nobody disagrees, then hopefully it is obviously a good idea. When there is disagreement however, there can be a discomfort in pushing ahead with something when not everyone is onboard. Finding comfort with that discomfort is part of the growing pains that come with growing teams.
Finding ways to make decisions without consensus that still make the team feel heard is hard, but necessary so that the team keeps moving forwards. Ideally you get to a place where you recognise consensus isn't coming (or not worth fighting for) and you can shortcut it without the dissenters feeling unheard or wronged.
One way to help structure this is to make it clear whether you are looking to debate or decide. Sometimes half the team are expecting to reach a decision and the other half are still in debate mode, trying to play around with an idea, poke holes in it and find better alternatives. When there isn't a clear goal to the discussion it's unlikely to go smoothly. "OK, that's been a good debate, now we need to come to a decision" invites everyone to switch to the same mode.
Another way to help drive a decision can be to seek clarity on how strongly someone feels. "I understand you don't like this idea but I'd like to go ahead with it. Is this something you can live with even though you don't agree with it?". Sometimes this is enough to make the person realise they are still in debate mode and don't really don't care that strongly about it. A good phrase for what you're asking here is for someone to "disagree and commit".
Sometimes you'll be the person pushing people to disagree and commit to your decision and other times you'll be the one having to do it. I think it's likely a measure of team health if you're finding yourself roughly in equal measures which side you land on here.
Not every battle needs fighting and recognising which ones deserve the most debate and airtime is important. You don't want to be debating which shade of blue to paint the door as the house burns down. Recognise there is an opportunity cost to decision making, whereby time spent on that discussion is time you are not spending building things, time not spending on perhaps more important decisions more worthy of your collective time and energy.
Ultimately, it requires a mindset shift that consensus isn't the goal per se. It isn't a failure when you can't find consensus; at a certain team size, consensus is just not possible. A lack of consensus is not something that should block you from making decisions.
