not living up to expectations

I'd use "let down".

Per MacMillan Dictionary:

to make someone disappointed by not doing something that they are expecting you to do

• The kids will be let down when they hear you can't come after all.
• The families of the victims feel that the justice system has let them down.

You can also use it for things, or for a new system as you describe, for instance:

The Apple event was a huge let down.

You could anthropomorphize it and describe it as an underachiever

a person (as a student) who fails to achieve his or her potential or does not do as well as expected [Merriam-Webster]

Similarly, you could say the system (or its proponents) overpromised

to promise more than can be delivered [Collins]

There are also colloquial phrases, such as missed the mark

to fail to achieve the result that was intended [Cambridge Dictionary Online]

1) Substandard "deviating from or falling short of a standard or norm" - In the same vein, you could say suboptimal and subpar.

2) Wanting "not having all that is needed or expected". Alternatively, you could use deficient, unsatisfactory.

3) Underperform "to be less successful than expected or required".