Is there a single word for something that is simultaneously not interesting and not boring?

Solution 1:

Bland may be what you are looking for, although it is generally used with the connotation of being boring https://en.oxforddictionaries.com/definition/bland

Solution 2:

meh According to Merriam Webster, meh is:

—used to express indifference or mild disappointment

First Known Use of meh: 1992

adjective

1 : not impressive : so-so ·a meh documentary

2 : apathetic, indifferent ·the movie left me feeling meh

The Oxford English Dictionary also lists meh, with definition very similar to that of M-W. However, the OED suggest an earliest use of "1928 or earlier." Meh has made it into the NY Times, as quoted by the OED:

2012 N.Y. Times (National ed.) 1 Nov. b13/1 Who else could they root for? The Chicago Bulls? Impossible. The Boston Celtics? Unconscionable. The team in New Jersey? Meh

and into other mainstream publications

2010 Time Out N.Y. 20 May 52/1 While this seems like an also-ran collection..even meh Picasso is better than a lot of the stuff out there.

The word is often uttered with a shrug of the shoulders and a deprecating expression on the face. I always assumed that the origin of meh was Yiddish, and was surprised to find, in meh, Wikipedia that its origin is speculative:

The origin is unknown. Some have speculated that the term's origin is Yiddish because of its similarity to the interjection "feh",[3] which appears in the 1936 Yiddish song Yidl Mitn Fidl. In Alexander Harkavy's "Yiddish-English-Hebrew Dictionary" the word is treated as a bleating or baa sound. Hooray for Yiddish, by Leo Rosten uses the word "mnyeh", which is speculated to be an early variant of "meh".

Solution 3:

What about tolerable especially in the second meaning below or its synonyms endurable or bearable?

tolerable

adjective

1.capable of being tolerated; endurable: His arrogance is no longer tolerable.
2.fairly good; not bad. 

Long distance running is tolerable.

Another possibility is mediocre

1. of only ordinary or moderate quality; neither good nor bad;
barely adequate: The car gets only mediocre mileage, but it's fun to drive.

The game was neither boring nor interesting; it was mediocre.

Solution 4:

I suggest 'prosaic'.

Merriam Webster defines it as:

Everyday, ordinary

It's not interesting - it's just the normal run-of-the-mill ordinary.

This answers, I think, all your criteria - 1, 2, 3 and 4.