What is a(n) conjunction/phrase/adverb that means the same as "if we ignore X, ... (the rest is good)" in writings?

Solution 1:

How about these options:

Disregarding the fact that the game lacks purpose, I think it's safe to say it's an amazing pastime.

Although the game lacks purpose, I think it's safe to say it's an amazing pastime.

I think one would normally use a simple adversative conjunction like although in examples such as yours.

Solution 2:

Also possibly "notwithstanding", which is slightly more formal:

Notwithstanding the game's lack of purpose, it's an amazing pastime.

https://www.wordreference.com/definition/notwithstanding

An alternative approach might be to add a concessive to the second clause, perhaps "nevertheless" or "in spite of this"

The game lacks purpose; nevertheless it's an amazing pastime.

The game lacks purpose. This notwithstanding, it's an amazing pastime.

The game lacks purpose, but in spite of this, it's an amazing pastime.

Some other ideas at https://www.wordreference.com/synonyms/notwithstanding