Liverpool getting out of the Champions League may be advantageous to them, but they shouldn't have left so quick when they have already given much effort from the beginning only to fall out along the line. Besides they were still topping the Premier League table before they fell out of the Champions League games but anyways, since they will be concentrating more in their Premier League games, it will give them an edge to draw closer to the title glory and it is becoming a reality for them already due to the point gap they are topping with.
Arsenal is not to be trusted in the Champions League because they almost put in same efforts as Liverpool did, except they will prove that they are prepared this time around if not it has always been same story for them whenever they appear in the Champions League so until they make improvements, they can't be hoped on to do anything in the Champions League games, Moreover there are still teams that are stronger than Arsenal so it will be difficult for them to scale through.
Aston Villa have been so loose this season in the Premier League but since they have also given some good display in the Champions League and got to the level they are now, they have also tried their best and even if they don't advance further, they have at least gotten the Champions League experience. There is a strong challenge in the 5th position in the EPL which means that Aston Villa may not have the privilege to reach the 5th position and qualify for the Champions League next season.
Regarding Aston Villa in the Champions League, yes they have really tried because even I didn't think they can get up to this stage of the competition, but the truth is, this particular stage might choke them but hey this is also football where anything can happen at any point in time. Liverpool didn't leave the competition at their own accord, they were eliminated and I see no advantage on them leaving at this stage, because it now this period that they were supposed to concentrate on the competition since they are 13 points ahead of Arsenal in the league with less than 10 games to go.
What helped Aston Villa was that they didn't meet much of bigger teams in the group stages, the only big teams they met was Bayern Munich and Juventus, they won Munich and played draw against Juventus. In fact, despite that they didn't face a lot of big teams, they really did a great job and i give kudos to their head coach Unai Emery for improving the club's performance recently. Despite that Liverpool was eliminated but it was due to their overconfidence in the Champions League that made them feel reluctant against Paris Saint German and they took the advantage and eliminated Liverpool and now they only have the Premier League trophy to work home with when they initially had 3 competitions they were supposed to at least win alongside the Premier League title.