I had the same experience (though I agree with other comments that the numbers are a little optimistic in terms of variance; I think there's a huge amount of variance in product work, you can't know what's a good investment until it's too late, many companies fail because of this, and there's huge survivorship bias in the ones that get lucky and don't initially fail). Slack spent tons of money in terms of product and engineering hours finding out what works and what doesn't. It's easy to copy/paste the thing after all that effort. Copy/paste doesn't get you to the next Slack though--it can get you to Microsoft's Slack-killing Teams strategy, but we obviously don't want more of that. And, obviously I agree with you about all the infra/maintenance costs, costs in stewarding API usage and extensions, etc. LLMs won't do any of that for you.

Absolutely, the moment I saw „95% of Slack core functionality” I stopped believing the author knows what he’s talking about

Students in the 2010s were building twitter clones as part of third-year college courses.

And somehow twitter survived and thrived and didn't really get viable competitors until forces external to the code and product itself motivated other investment. And even then it still rolls on, challenged these days, but not by the ease of which a "clone" can be made.

Yeah, I can build a Slack "clone" in a couple of weeks with my own two hands, no AI required. But it's not going to actually be competitive with Slack.

Just to pick an incredibly, unbelievably basic enterprise feature, my two-week Slack clone is not going to properly support legal holds. This requires having a hard override for all deletion and expiration options anywhere in the product, that must work reliably, in order to avoid accidental destruction of evidence during litigation, which comes with potentially catastrophic penalties. If you don't get this right, you don't sell to large corporations.

And there are hundred other features like this. Engineering wants an easy-to-use API for Slack bots. Users want reaction GIFs. You need mobile apps. You need Single Sign-On. And so on. These are all table stakes.

It was a cliche for many years that Microsoft Word had "too many features." So people would start companies to sell "lightweight word processors" that only implemented "the most used 20% of features." And most of these companies sank without a trace (with a couple of admirable exceptions that hyperfocused on specific niches). Google finally made progress against the monopoly, but to it, they actually invested in a huge number of features.

Believe me, I wish that "simple, clean" reimplementations were actually directly competitive with major products. That version of our industry would be more fun. But anyone who thinks that an LLM can quickly reimplement Slack is an utter fool who has never seriously tried to sell software to actual customers.

Also, it's obviously faster to copy Slack 1-to-1 than inventing it from scratch. Making Slack was not just coding.

Human slop think-pieces.