There is a fundamental difference between projects worked in parallel or in series yet both have their merits.
In the former, multiple tasks and projects are tackled at the same time while with the latter, every step follows the next.
Each of us operates at different levels with respect to how we handle projects. Some are most comfortable focusing all their efforts on a series project: dig in, push everything else aside, focus on seeing every step in the process completed to fruition. Others work effectively on multiple tasks and projects by commutating in small spurts their time and energies into many projects. Still others operate in a combo between both series and parallel.
Neither method is better or worse than the other. It's up to each individual to figure out the most efficient path for their particular skills.
Take PS Audio as an example. At any one time, we have multiple projects being worked upon: speakers, streamers, amplifiers, DACs, recording studio, Octave music, etc. Yet, within each of these parallel endeavors, we find a dedicated group of engineers working tirelessly in series: the beauty of having a team.
Me? If I don't have ten projects percolating in my head I am bored. My greatest joy is commutating between projects and diving into each with all the zeal and passion I possess until exhausted, then moving on to the next and repeating.
What's glorious about our differences is recognizing within each of us what works and doesn't.