I think you need to counter more often and use down or up smash for example if an enemy is too close there is a hit box on lucina's and Marth's feet for up smash and its pretty good for aereals which you dont do too often, also more off-stage and I've seen the video and shield breaker could have been used a lot of times. just an opinion dont get mad ^^
The BeBop From more professional Lucina players, I'd expect to see a more offensive off-stage play and actively countering the enemy's recovery. Also you should try to use Dancing Blade or Shieldbreaker when descending to the ground to get rid of all landing lag. And yeah, I think I'd use the forward smash less frequently in favor of Shieldbreaker