They work better than databases for accessing databases - nsl.com has examples like tables.k , a reasonably efficient in memory ordered-and-mostly-relational database in all of 14 lines of K.

And a variety of spreadsheets, from 2 to 100 lines.

They were sort-of-ok for API access, but Shakti’s FFI is actually incredibly straightforward - comparable to writing a C extern definition only much terser (‘cause it’s Arthur...)

APL isn't always written (⊂∘⍋⌷⊢), APL has a traditional notation which is like other procedural languages:

    :If databaseResult.Rows.Count > 5
    :AndIf warnOnLargeData
        
        :For Row :In databaseResult.Rows

            logToFile 'Careful, that's a lot of data, e.g. ', Row[1]

        :EndFor
    :EndIf

and Dyalog APL is a .Net language, which has extended this style with :Namespace and :Class and :Access and :Signature ways to build objects and methods to make your API and export it as a .DLL for use by other .Net languages, or plugin to ASP.Net and make a web service[1], or accessing most things C# can[2], e.g. if you want to use a System.Collections.ArrayList it's right there:

          ⎕USING←'System' 'System.Collections'
          arr←⎕NEW ArrayList
          tmp←arr.Add ⊂'Test'
          tmp←arr.Add ⊂'Hello'
          tmp←arr.Add ⊂'World'
          arr[0 1 2]
    ┌────┬─────┬─────┐
    │Test│Hello│World│
    └────┴─────┴─────┘
          arr.RemoveAt 0
          arr[0 1]
    ┌─────┬─────┐
    │Hello│World│
    └─────┴─────┘

and that means things like System.Data.DataTable and SQL Connections for your database access. .Net isn't as popular as JavaScript and Rust, but it is a pretty large, stable, capable and established ecosystem to be able to hook into.

The core of APL symbols more or less /are/ an embedded language in the wider APL, just that wider APL is not showy for codegolf and is not unusual and pretty symbols, and you can't use it /without/ the symbols.

[1] See the examples shipped in the install folder like "C:\Program Files\Dyalog\Dyalog APL-64 18.0 Unicode\Samples\asp.net\webservices\"

[2] I expect not /everything/ C# can; C# is the first-class .Net language, but if you have things written in C# you can use them.

What makes them bad for APIs or databases? Both k and q are very practical general purpose languages (J and APL less so) that would be an appropriate choice for almost any kind of app, imo.

q especially looks mostly like a normal procedural language, and can be used like one too.