I disagree. I really enjoy TDYD as someone who's been running around with Last Word for awhile.
TDYD is supposed to be used for hip-fire headshots, like TLW. So unless you're hitting headshots consistently yeah, 5 shots is a bit paltry.
Handcannons are supposed to be high-risk/high-reward hence TDYD's low magazine size with Final Round and why Clown Cartridge only procs 1 extra round--anymore would nullify the utility of Final Round.
TDYD is a handcannon for one who is already proficient with a very-particular playstyle concerning HCs, and I can see how it might not be for everyone.
That doesn't mean however that it's a bad weapon--just very niche.