Engineers frequently try to be like "bro your site won't scale to 10000 users" and guess what? Nobody cares, nobody working for their company of 100 people is even thinking about what hire #1000 looks like. Not every company needs Slack level scale.
People have spent so long over engineering for scale, they often forget a 3 tier application can survive 99% of companies for over 5 years untouched.
But, as people have been saying since shortly after "Big Data" was the buzzword whose shoes AI now fills: it's not "big" data if it fits on my laptop.
Even if the team does care, 10k users just isn't a particularly difficult goal.