Roberto Martinez's men were pushing for the final UEFA Champions League place before three losses in their past four left them having to settle for fifth.
A spot in the UEFA Europa League shapes as an opportunity for Everton to continue improving, according to 27-year-old Naismith.
"Europe definitely gives us a chance to keep progressing," Naismith said.
"If you are not involved in it, you end up sitting there watching, so it’s much better to be a part of it and have a chance of winning a trophy.
"I'm sure we'll work on that and strengthen the squad in the summer. We have got to grips with the fundamentals of what the manager wants us to do and we have to refine that."
Naismith has scored five league goals this season, with most of his 30 appearances coming off the bench.
The former Kilmarnock and Rangers striker said dealing with critics was something he had become used to.
"At every club I've been, I've had doubters and had to deal with that," Naismith said.
"You have to get your head down and work hard, and I’m glad that over time I have started to change some people’s minds.
"There were certainly doubts about me when I first came here, I have had to come through that. And I admit that last season I probably didn’t show anywhere near what I am capable of.
"I knew I was good enough and I knew I could bring something to the squad, so I just had to stay strong and keep believing in myself."
‘After Manchester City’s recent form, maybe they’re the underdogs against Manchester United!’ Former Red Devils defender on this weekend’s derby
‘Arteta, Alonso, Emery, me… none of us were physical players – we needed the understanding of the game. That probably helped us move into management’: Premier League boss reveals reasons for natural career progression
