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

Question

I am looking for a word that would describe a concept or activity, such as playing a game X, that is¹ neither boring nor interesting. In other words, it should mean ‘neutral’ wrt intrestingness (~ boringness) but still comparable on the scale of intrestingness to both ‘boring’ and ‘interesting’.

An example sentence would be

As far as I'm concerned, long-distance running is [insert word]; it is not boring but it's also not interesting.

Criteria²

1. Has to be unambiguous³, and may consist of two words at most.
2. Has to be a single word.
3. Should be formal in the sense that it is included in Cambridge Dictionary, or Merriam Webster, or both.
4. Should not contain negating prefixes, such as ‘un-’.

Does such a word exist in the English language?

For readers' convenience, please state which criteria you believe your word suggestion has met. You may do so, e.g., by adding a disclaimer at the top or bottom of your answer. Simply writing (1., 2.) is sufficient.

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¹ Assume a ternary system of intrestingness.

² If not all criteria can be met, you may relax the requirements from bottom to top, in the following order: 4. -> 3. -> 2. -> 1. Answers with the smallest number of relaxed criteria in this order will be preferred in accepting. For example, fulfilling (1., 2., 3.) is better than achieving (1., 3., 4.). Situations where a higher priority ordering fulfills fewer criteria than a lower priority vector, such as (1.) vs (3., 4.), will be assessed on a case-by-case basis.

³ Words such as ‘unappealing’ thus even fail criterium 1 because in a three-valued system ‘unappealing’ ~ ‘not appealing’ ~ ‘not interesting’ can be taken to mean either ‘boring’ or ‘neutral wrt intrestingness’.

Answer 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

Answer 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".

Answer 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.

Answer 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.

Answer 5

I would go for unremarkable:

unremarkable
adjective

Not particularly interesting or surprising.

his early childhood was unremarkable
an unremarkable house

Pronunciation: unremarkable /ʌnrɪˈmɑːkəb(ə)l/

It doesn't carry the connotation of boring and is by definition not interesting.

If it HAS to not use the un- prefix, then I'd go for common:

common
adjective

1.3 Ordinary; of ordinary qualities; without special rank or position.
the dwellings of common people
a common soldier

Pronunciation: common /ˈkɒmən/

Maybe even basic:

basic
adjective

1.1 Offering or constituting the minimum required without elaboration or luxury.
the food was good, if a bit basic

Pronunciation: Basic /ˈbeɪsɪk/