Aston Villa have performed very well this season. And finally the team qualified for the Champions League. But in the last few matches of the season we don't see good performances from Aston Villa players.
Aston Villa have the ability to challenge for the Premier League title. This team is strong and the players are very confident. However, several weaknesses in the Aston Villa squad are quite visible. Aston Villa's defenders have not fared well this season. .The team has conceded 61 goals in 38 games. If Aston Villa wants to do well in the next season, then the defense must be strengthened by the Aston Villa team. If the defense is not strong, Aston Villa will not be able to be in the top four of the table next season.
Atleast they were far more better than Chelsea and Manchester United, I appreciate their efforts. Aston Villa fully understood that they can't win the title or end the season as a runner up, so instead they maintained their 4th position on the table just to qualify for the Champions league. The team should try to improve, it is not just all about qualifying for the Champions league, are they competent enough to compete in the league because it will be very tough as most Champions from other leagues will us be competing, just as you said about their defence line, they should kick off enhancing it, I really want to see them do better coming season.
If Aston Villa dreamt of winning the title last season, I will call that being greedy, so I love the fact that they settled for what was possible then and see what the future holds for them. I can say that they are a work in progress and from this season's champions league, they will be exposed to the real European competition and that have a great way of making them stronger and better. Last season could be used as a test, and they passed so well as they were able to displace some of the big names you mentioned to secure a position at the champions league.
However, what I find disappointing was their conference league performance which they lost woefully to Olympiakos that later won the trophy. I expected they would be able to scale through to the final and hopefully win that league. I know they would have learnt some lessons from that outing to be better next season.