Sampson did not select Aluko, 30, in his 23-strong squad for Euro 2017, despite her being last season's Women's Super League top-scorer.
She last played for England on 12 April 2016 against Bosnia & Herzegovina.
"For all my life I've always looked at performance to justify rewards you get," Aluko told BBC Radio 5 live.
"Sports people, athletes, young people, anybody in life - the message and values the England team represents should be about hard work, putting your best foot forward and getting rewards for that.
"Mark Sampson has publicly said he doesn't pick on form so the other criteria [are] popularity, team dynamics and character.
"The message this is sending out is if you are popular with the manager you get into the team. You don't have to perform.
"It's a dangerous message to send out, particularly to young players."
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This is the first time in 12 years that Aluko has not been selected by England for a major tournament but she said she was not surprised to be left out.
"After winning the golden boot last season and still not being selected it was obvious to me that the door is shut and has been shut on certain players for a while now," she said.
"I haven't spoken to Mark Sampson in over 12 months. He has said publicly the door isn't shut so I'm really intrigued to find out how that door can be opened again."
Despite her own disappointment, Aluko is hoping the team do well in the 16-team tournament in the Netherlands, where they have been drawn in a group with the hosts, Germany and France.
"I'm delighted for my team-mates who have been selected and I'm excited to watch them in the summer," she added. "I'm certainly behind every single player and supporting the team to hopefully do well in Holland."
Chelsea forward Eniola Aluko says England manager Mark Sampson's policy of not picking his squad based on form sends out a dangerous message.