Lifting a light weight slowly uses more energy than performing the rep at a regular pace.
Now if you’re just talking about getting super tense and running through the movement with maximal tension and not purposely turning it into a 5s negative and 5s concentric then okay yes that good.
Purposely lifting weights slowly just teach you to lift weights slowly ( specifically as it relates to a compound main movement ). Say for example your work weight is 315 for the day. If you do bar through 275 overly controlled and slow your 315 is going to move with less force than it would if you just performed normal reps. You can measure this with a tendo unit.
However if it is working for you and you’re making progress I can’t really argue with results.