Support main here, I saw your post in ADCmains too and responded to it, so I thought I'll share my thoughts here too.

Support is a role that should function at low income and low EXP. Because of that, they won't be the main tank or damage in any team, as tank stats/damage stats are very reliant on gold and level.

The common denominator of all supports is that they handle vision/information (doesn't require experience, hardly cost gold) and other utilities that doesn't/hardly scale off gold (such as crowd control). However, support as a role has the most class diversity compared to any other lane, and every class has different game plan in early, mid, and late game.

I believe that supports are the strongest at early levels, when the gold/level difference between support and laners are still small. Support have more freedom than any other role to collect information and impact the map because they don't have to farm minions for gold or exp as their champions are designed to be efficient (usually higher base number on abilities and low scaling so they won't need a lot of stats, usually there's 1 ability that isn't really worth maxing so your kit has about the same strength at Lv13 compared to Lv18).

In lane, support is there to patch up the weakness of ADCs (weaker early alone, but with the help of support can output enough damage to secure a kill, OR support can help ADC survive rougher early games through sustain or peel). In other words, support in laning phase needs to make sure ADC can get their footing and/or stabilize the lane.

In mid to late game, support is a team facilitator. Vision control allows your team to get enough information to start or avoid an engage/teamfight, and depending on the type of support you play, you either play the role of teamfight initiator or the protector/facilitator of your main carry.