@matigo Newer macOS (Catalina and later) has gotten more clever. It will just not charge up when it’s mostly attached to charger:
Your computer temporarily paused charging to extend the life of your battery. Your battery may drain to 90% or lower before it begins charging again. If you need to immediately resume charging, you can turn off battery health management in Energy Saver preferences. https://support.apple.com/guide/mac-help/if-your-battery-status-is-not-charging-mh20876/10.15/mac/10.15
I’ve replaced a couple MacBook batteries. It was not too bad. iFixit is a big help.