If you don't rely on the presence of a form designer then you might want to use Visual Studio Code with the OmniPascal plugin (http://www.omnipascal.com) as a replacement for the Lazarus code editor.
> The IDE is just so far behind the competition. Crashing all the time an slow. Theming support ist very limited (to date). Delphi Code Insight ("Intellisense") is slow and sometimes just refuses to work and is generally not on par with other offerings
I'm 100% with you. That's why I switched from Delphi IDE to Visual Studio Code with OmniPascal (www.omnipascal.com). It's much nicer to work in a state-of-the-art editor.