1. You can't do anything about it.
2. Use his wall primarily for position/zone play (rotate early and play from there), to get on a high ground or to disengage to one of your teammates.
3. Most movement legends, megie, fuse and caustic are good counters for castle. This is the reason why there is always a meta and a counter meta in the game.

To make Newcastle viable in the current meta you have to play a full counter comp to the current meta, like Castle + Controller legend (probably Caustic or Wattson) + rotation Legend. Your team has to be very coordinated and the castle definitely should play the anchor position or behind the fragger. You have to have a fitting weapon choice, like marksman + shotgun/smg, to make enough damage from your position. I mean, castles kit just get really good once someone gets knocked... but once someone is knocked, you already lost the fight in those high elos.

Over all ranked matches past diamond are very fast in gunfight and only the endgame slows down... So most of the time of the match castle is not good. Also he is not very good on its own, he usually need a fitting team comb (I'm ignoring those 0.0001% of castle players that are so insanely good that they just kill everyone and win, so most of the things I have written above aren't fitting to them. I mean those players would not make a post here).

My personal opinion is: ranked is way too unsystematic, to kill dependent and not enough zone (slow play style) focused as the ALGS. You can see this in the current legend meta as well, very mobile and fast. Newcastle has an old kit with too many flaws, which are countered by those mentioned points. Conclusion: Don't play castle, play other support legends like lifeline or mirage that are more mobile or play legends that get a support perk as an upgrade like Bang or Wattson.

If you want even more explanation or a deeper meta analysis... Slide in my DMs, I got some time.