In laws are not supportive of wedding

We are getting married in August of 2021. I turn 40 this year and my fiancé is 43. Neither of us has ever been married and we do not have any kids. My fiancé’s family does not believe we should be having a wedding and should just elope, because of the cost. We have not asked his family for any help financially towards the wedding. My family has offered to help. Whenever I bring up the wedding to his sister or parents they are always negative and don’t seem to think we deserve to have a wedding day. It’s been really stressful planning a wedding during a pandemic, but we feel by our wedding date the vaccine should be widely available. Our wedding is at an outdoor venue. The response from my fiancé’s parents and sister have really been hurtful to him and myself. Is it too much to ask for them to either keep their negative comments and opinions to theirselves. All they are expected to do is show up. His sister is standing up in the wedding and any time I bring up wedding plans, she changes the subject or says things like “you guys should just elope”. This has been very disheartening and I’m not sure how to address this.