As a general purpose development tool, Lazarus can build almost or maybe all kinds of software you ever know, if you have the knowledge and skills. Web development, no problem. But if you're a web developer, you probably will choose those tools specially designed for web. Mobile device apps, Lazarus can build too. If you just started a new company for developing commercial mobile apps, will you choose Lazarus? That will be a risky decision for your company.
Lazarus can build PC games, we know it for sure. Someone ever asked me, why I didn't just use xyz tool instead of Lazarus. I use Lazarus because I like solving problem, I know Pascal and I like playing games. My goal is not developing games but doing research. But what they said is absolute truth. If I use Unity, Unreal Engine, Game Maker, Cocos, etc, I now should already have built plenty of games.
So Lazarus as a general purpose development tool, has a double-edged sword effect.
Also software popularity is very dependent on the big company who is sponsoring/maintaining it. Pascal gained huge popularity in the Borland era. Unfortunately Borland lost the battle to Microsoft. Recently, Google introduces new programming languages/tools. Good or not, like it or not, there always huge numbers of users want to try it. Because the big company is recommending it.
Because of there isn't any big company is sponsoring Pascal currently. Actually, yes it is. Embarcadero, unfortunately it is dying and having bad reputation - too pricey. Lazarus/FPC/Pascal is not widely used. Big software project requires huge efforts and money. If it is a open source project, big project needs big company sponsoring it. If it is a commercial project ... well ... many commercial companies are more interested in using other development tools.