Nice. Your pulldowns are kinda low at 1k as your source needs to provide 5mA (at 5V). 10k or so might be gentler. Also, with HC parts, your source signals need to be 5V logic. Alternatively, you can use HCT parts and allow it to work with either 5V or 3.3V input signals.
Actually I was talking about adding a series resistor to provide some esd protection since you are running these signals off on wires somewhere, but yes, pullup or down is needed as well as you cannot have a floating cmos input. It seems like a lot of extra parts but you don’t want to zap the chip. Static zaps are common here so I am a bit sensitive to it. You can add other protective devices, but the simple series resistor (in conjunction with the protection diodes inside the chip) helps limit current when there is a transient spike that exceeds the rails. I have used a series resistor from say 1k to 47k – the cmos input is very hi-z so it does not affect normal operation.
From a nexperia hc guide:
Also, you don’t really care what you shift into the data-in as you are just shifting 16 times to read the input data.
If you later add a 595 or two then you need to properly set/clear bits at the correct point in the shifting, and another signal to load the output regs. A fun little project.
Speaking of 595s:
sprig’s led gizmo