Tsk, tsk. So many young whippersnappers around these days, who haven't read 'Fate is the Hunter' by Ernest K Gann.
If you think seasonal commands is something new then you really should read the book. Nothing has changed in this business since those early days of airline flying.
Until seniority is abolished as a standard for deciding who is next in line for command assessment this will continue. Is it bad? Per se, probably not as it does give eligible senior effoh's the chance to experience the responsibility of command.
When the good times roll on, they'll be well prepared for the job and eventually they'll have a big enough cushion of more junior pilots to keep them comfortably ensconced in their lofty position of responsibility.