If you're using a more recent Android device you'll definitely notice the Adaptive Battery feature built into the battery settings. This feature limits battery usage to apps that are not always active. In addition, another feature to keep the battery healthy is to limit the charging power when sleeping and will only finish charging after waking up.
This feature was introduced for Pixel users through Adaptive Charging. When this feature is given to Pixel users it is only active if the user has set an alarm only. Recently some users have noticed that if there is no alarm set the device still cannot be fully charged quickly.
Google is seen quietly updating this feature to limit charging power based on user device usage patterns. This is a frustrating thing for some users who can't enjoy fast charging and want to keep the battery healthy at the same time.
Google still does not explain why this change was made. Making the alternative to the user is to continue deactivating this Adaptive Charging feature. This feature is already available on iPhone devices with the "Optimum Battery Charging" feature, lower BBK Electronics devices (Oppo, Realme and OnePlus) through "Wise Charging" and other manufacturers also offer more or less the same feature.