why do you let people who are level 30 and doing their placements play against golds/plats

The MMR system is really hard to manage I get it but can we plz stop having games where one side feels completely lost when they have 2 lvl 30s and they have to play against gold/plat players, i know their isn't much of a difference between bronze and silver, gold is only slightly a step with most plats being much better than anything mid silver and under. They really need to limit lvl 30s to ranks such as high silver and below. When the lvl 30 has very little understanding of the game compared to a gold/plat player it seems like the game is one sided almost and you cant do that much to help them since they don't want to be helped. In higher elos such as diamond and above its somewhat understandable that you get diamonds in master games or even the rare D5-1 in challenger since the number of players is more limited in those ranks but lower elo shouldn't have to deal with fresh out the gates players that have like 3 or 4 champion they like to play and think that ranked would be easy for them to play despite not knowing proper builds or how to utilize the champion properly. The gap just seems a bit unhealthy.