This focuses the fact, that some operational amplifier have diodes (or similar) connected between inputs. In such a case, any positive voltage greater than 0.7V at input 'Vin' would be shunted to ground by these diodes (within A1).


Unfortunately not! The reason is 'common mode input voltage range'! Input voltages must be some volts higher than negative supply voltage, in your case 0V. So, this old TL084 cannot be used in your circuit. Even if supply voltage would be a bit higher, single supply operation with TL084 would always mean to work with a concept, where inputs are forced to about half the supply voltage by additional circuitry.
TL084 was designed for +-15V operation. It can very well be used even with +-5V operation, but then only very little signal voltages can be handled, as voltages at inputs and output must stay some volts away from supply voltages. But with +5V single supply voltage a TL084 shouldn't be used. All the internal stuff, like current sources, current mirros, etc, aren't turned on at that low supply voltage. Using the TL084 here wouldn't be very useful.

Kai