Personally, I like IoT things on 2.4. Most need very little bandwidth, and 2.4 has a better, longer, more stable range, but lower speed potential. That longer range can cause signal interference with neighboring AP’s. Newer more powerful radios are blasting out incredibly strong signals to allow a single AP to cover a whole house, but that sometimes just clogs up the airways.
There are a number of wifi analyzer apps you can download to check the congestion in the airways, and like @millie said, change the channel on your 2.4 to one of the less congested channels.