ETH network activity is low. What could it mean?

The amount of daily active addresses + the amount of new addresses (wallets) added to the Ethereum network lately is rather low.

But is it necessarily bad (for the ETH price) ?

I don't think so. These both metrics has been proved to be "lagging indicators".

Means - only after the price makes decisive move up these two metrics starts intensively growing.

The low or values of DAA and Network Growth could be rather seen as a good way to accumulate, as they show "the lack of speculative interest" (read - crowd is passive, not yet excited).

One addition though - also the "social attention" should be rather low to make it good entry point. The basic check would be "social volume" metric. For Ethereum it can be found here: https://app.santiment.net/projects/ethereum?from=2019-07-07T15%3A00%3A00.000Z&interval=12h&isShowAnomalies=false&metrics=historyPrice,socialVolume&scale=time&slug=ethereum&title=Ethereum%20%28ETH%29&to=2019-10-08T15%3A00%3A00.000Z