VCC sets the voltage

The switch joins two wires

The switch has two sides. One goes to VCC. The other goes to SIGNAL. Pressing it joins them, with a contact resistance the switch's drawing puts at no more than 100 mΩ, which for this purpose is a plain wire.

So while the button is down, SIGNAL is VCC. Put 5 V on VCC and your pin gets 5 V. Put 3.3 V on it and your pin gets 3.3 V. Nothing on the block changes the level in between.

3V3 beside a 3.3 V board

An ESP32, an ESP32-S3 and a Raspberry Pi Pico run their pins at 3.3 V, and none of them is built to take 5 V. Pick 5V in the figure with one of them selected: it reads HIGH, the button works, and the pin is past its rating every time you press. That damage is slow and it does not announce itself, which is why the wiring is the rule rather than a suggestion.

Connect VCC to the board's 3V3 pin. The block works exactly the same from it, and the only thing that changes is that the red LED is a little dimmer. The light on the board works out by how much.

5V beside an Uno

The Uno's pins run at 5 V, so its 5V pin is the right supply. 3V3 would work too: the ATmega328P reads anything above 3.0 V as HIGH. But that leaves 0.3 V of margin to gain nothing, so use 5V.

VCC left off

With VCC unconnected, the switch has nothing to join SIGNAL to. Pressed or not, the pull-down holds SIGNAL at 0 V, and your pin reads LOW forever. The red LED does not light either, which is the quickest way to tell this apart from a sketch problem.