A lot of things that Foglight does could be derived from DMVs and extended events. I'm going to sound like a salesperson, but I have to be a salesperson to sell the value of a product to my company. They need to understand that to answer some of the questions they ask, not having a tool like this will make my answers very speculative.
As a DBA, you have to be able to answer three questions. The first is: What's happening right now? Why is the system slow or why are things not responding? That is probably the most trivial for an experienced DBA. That is where the tool's value might not be as obvious, as you can look at the sp_who or DMV and pretty much tell what's going on without having to pay money for a license for a product like Foglight.
The second question is: What just happened? There could be just a couple of seconds difference between the first and second questions. But the effort to answer the second question is significantly higher because it is water under the bridge. You need some kind of monitoring solution implemented, even if it's just a basic solution where you capture a certain timeframe, so you can roll back and review what just happened. However, there will still be a significant amount of speculation because, usually, you can't afford to monitor every single metric, and there are hundreds of them. The issue could be the OS, it could be infrastructure-related, or it could be that the SQL code is not performing well because it's not written well. So the second question is significantly harder to answer, and that's where a tool like this will become very helpful.
The third question is: What has been going on? That is by far the hardest question to answer without this type of tool. This is the type of question a manager might ask for the purposes of resource planning. Or a senior VP might say, "Hey, how are we doing? Can we bring on another customer? Can we sustain a 20 percent increase in workload?" I don't know how I would answer that question without having this type of solution. I work in the industry quite a bit and there is, unfortunately, a lot of misunderstanding due to a lack of a comprehensive view of infrastructure.
There's no way to answer that question without getting some kind of baseline tool. Unfortunately, in most of the shops I work for, only one question is usually being answered relatively accurately, and that is "What is going on?" And it's a luxury because by the time a customer escalates an issue and it gets interpreted by support people, there's a gap. That gap could be a couple of minutes, a couple of hours, or a couple of days.