I think we all realise the EU has weaknesses and there are many areas for improvement. However, we have every right to change our mind now that we are seeing more clearly some of the implications of leaving and witnessing the UK Gov's failure on many fronts, including their inability to have meaningful trade talks with other countries (instead alienating them at an apparently ever-increasing rate!).
TM's position that it would be undemocratic to change our mind just doesn't hold water. Consider a family group who "voted" in January, after considering options, to go on holiday in June to a new resort after studying the prices, facilities and pictures in a glossy brochure. They then find out in May from someone who has been ( and has the photos etc to prove it) that the hotel is half-built, has no swimming pool, 80% of the guests have suffered food-poisoning and it is 2 km, not 200 metres, to the beach. Would they agree to go anyway as it would be undemocratic to overturn their original choice?
Brexit poses such a risk to the economy, health, safe food supply, and much more for generations to come that it would be lunacy not to reconsider.