Dealing with Mr fantastic as Venom

Howdy y’all! So I don’t get a whole lot of time to play and currently sitting at plat 2 but along the way I have noticed a hole in my game play

I am a vanguard main with most of my time on venom this season, I have had a few games where a Mr fantastic has just bullied or support, often upon realizing this I switch to Groot to give us a strong front line, when I do I feel a struggle to gain any ground, I can do it but it’s a slow crawl. (Spend a lot of time keep him off my support with my walls it works but I have to give space to do it then retake the space again- it time consuming)

I would really like some tips for dealing with Mr fantastic specialty as venom, even if I attack him to try to peel for my support he just powers through and get a pick on the support then dies or back off - I am have not yet been able to figure how to deal with that as venom- any tips or ideas would be greatly appreciated