Characterisation and subsequent development is a little weak. Acting is good, with Schwarzenegger and Hamilton doing a fine job in support of the new cast. The social commentary is a little shoehorned. The early action sequences are excellent.
Look out for an early sequence which features some very impressive de-ageing. I'd have happily watched a full film like this - ala The Irishman and Captain Marvel. The technology is progressing in leaps and bounds.
I find it hard to rank the later films in the Terminator series. I'm the rare person who really liked Terminator:Salvation. Terminator 3, for all its jokiness closes the story off satisfactorily. Terminator: Dark Fate are their equal for different reasons. Terminator: Genisys has some wonderful ideas and its alt-universe greatest hits is a lot of fun - but I can't get past the miscasting of Jai Courtney and Jason Clarke, the total lack of chemistry between Emilia Clarke and Courtney, nor his appalling acting.
Verdict: Back for more.