The ability to forget certain things is important. Knowledge advances by rejecting false theories.

Scientific and engineering knowledge fits together because reality is consistent. So it isn't necessary to memorise everything.

Rather than trying to 'drill in' certain pieces of essential info, it's better to improve the state of your mind, so that your memory works better generally. We waste a great deal of vitality by overeating, watching TV, etc. It seems to dull the mind and the memory significantly IME.

Forcing yourself to memorise stuff that doesn't interest you will tend to shut the mind down. It's like being at school.