There was a time when Gilbert & George made provocative pictures that probed the body politic for sore points that others preferred to ignore. Trawling the streets of East London, where they’ve lived since the 1960s, the artist duo chronicled the poverty and squalor of their neighbourhood in large photographic panels that feature the angry, the debased and the destitute.

It’s been a long time since an exhibition made me feel physically sick. The Hayward Gallery is currently hosting a retrospective of the Japanese artist Yoshitomo Nara and the combination of turquoise walls and oversized paintings of cute kids turned my stomach over. Kitsch has that kind of power.

On walking into Mikalene Thomas’s exhibition at the Hayward Gallery my first reaction was “get me out of here”. To someone brought up on the paired down, less-is-more aesthetic of minimalism her giant, rhinestone-encrusted portraits are like a kick in the solar plexus – much too big and bright to stomach. Could I be expected to even consider accepting these gaudy monstrosities as art?

Under the guidance of director Ralph Rugoff, the Hayward Gallery seems hell bent on reducing art to the level of fun for all the family. And as though to prove the point, cretinous captions strip the work of all meaning beyond the banal, while press pictures showcase kids gazing at large sculptures.

A polar bear stands guard over the seal pup it has just killed (main picture). How could photographer, Hiroshi Sugimoto have got so close to a wild animal at such a dangerous moment? Even if he had a powerful telephoto lens, he’d be risking life and limb. And what a perfect shot! Every hair on the bear’s body is crystal clear; in fact, it looks as if her fur has just been washed and brushed.

Dear Earth, Art and Hope in a Time of Crisis is a mixed show of artists who address the parlous plight of our planet. The issue obsesses me, so anyone who braves the pitfalls of exploring this difficult subject has my sympathy.

Entry to Mike Nelson’s Hayward Gallery exhibition is through what feels like the store room of a reclamation yard. Row upon row of Dexion shelving is piled high with salvaged building materials including old doors, ancient floorboards and wrought iron gates, while even more gates and doors are leant against the walls.

Louise Bourgeois didn’t throw anything away and, during the last 20 years of her life, she used her own and her mother’s old clothes to create theatrical tableaux which revisit painful childhood memories. “These garments have a history,” she explained. “They have touched my body and they hold memories of people and places. They are chapters from the story of my life.”

In 2015, an abstract painting by Gerhard Richter broke the world record for contemporary art by selling at auction for £30.4m, and the octogenarian is often described as the most important living artist. But I’ve always found the prices fetched by his work baffling and the claims made about him exaggerated, since his paintings leave me cold.

The 31 artists in Mixing it Up all live in this country, but a third of them were born elsewhere – in countries including Belgium, China, Columbia, Germany, Iraq, Zambia and Zimbabwe – and they’ve brought with them immeasurable cultural riches. The exhibition is like a snapshot of pre-Brexit Britain, a reflection of the days before we changed from being a relatively friendly, open society into a grumpy, insular backwater.