Unable to contribute due to legacy toolchain 'DynamicJsonBuffer is a class from ArduinoJson 5'

[nuschpl]

Hello
I've tried to follow the guide and add depdendencies:

    ArduinoJson library 5.13.1 by Benoit Blanchon
        https://github.com/bblanchon/ArduinoJson
    ESP8266FtpServer.h
        https://github.com/exploitagency/esp8266FTPServer/tree/feature/bbx10_speedup

Added the first lib directly from Arduino IDE, and the second via exported ZIP file of above URL. This resulted in compilation error:

In file included from /Users/User/src/ESP-RFID-Tool/Source Code/esprfidtool/esprfidtool.ino:605:
/Users/User/src/ESP-RFID-Tool/Source Code/esprfidtool/api.h:43:11: error: DynamicJsonBuffer is a class from ArduinoJson 5. Please see https://arduinojson.org/v7/upgrade-from-v5/ to learn how to upgrade to ArduinoJson 7
   43 |   DynamicJsonBuffer jsonAPIbuffer(bufferSize);

So my question is are those custom library variants really needed, can we make anything that software will be more maintanable ? I'm Arduino newbie but is there no way to add those dependencies as a reference to Sketch file instead of encouraging developer to manually do so ? This way this could could still be contributed