The tablets have nothing fancy in them other than some dyes, they are just soap at a mark-up. Even the cheapy store brand stuff does just as good of a job.
Additionally, depending on the hardness of your water you may need less detergent than the tablets have in them which could leave a white residue on your dishes.
Finally, with the powdered detergent you may need to sprinkle a little in the door for a pre-rinse which you can't due with the pods. Check your washer instructions.
Since first lockdown in my country, when dishwasher tabs went missing in stores, I got used to use 1/2 a tab for each wash. Turns out dishes were just as clean as with a full tab. To this day I keep using 1/2 tab per wash.
To push your example even further, I once forgot to load anything and Imagine my surprise when I opened the dishwasher and everything was really clean, maybe except one plate.
Additionally, depending on the hardness of your water you may need less detergent than the tablets have in them which could leave a white residue on your dishes.
Finally, with the powdered detergent you may need to sprinkle a little in the door for a pre-rinse which you can't due with the pods. Check your washer instructions.
P.S. Never use liquid detergents.