I would say it was a combination of both. Whilst neither film was bad, they weren't great either. They were just short of average. If NEM had good critical reviews and madea decent sum of money at the box office Paramount would have made another film.
If you look at the TOS movies generally TWOk, TVH and TUC are considered to be the best of films. Whilst TMP, TSFS and TFF are considered the weaker. So you had one weak, followed by one good. Whilst for the TNG films, FC is generally conisered to be the strongest whilst the other three the weaker films.