I think you need to differentiate between flippers and people purchasing to rent them out.
Flippers buy, spend some money to theoretically raise the sales price, and sell – in a short time frame. They don’t plan to hold the house, their business model is get-in-and-get-out.
Landlords buy with a different criteria – they look at cash flow vs expenses.
What seems to be the underlying issue isn’t whether they are flippers or landlords – it’s that these houses are being bought by people other than you.
My only advice – keep saving. Keep looking for opportunity to purchase a good value. If you keep getting outbid – perhaps you can’t afford the house. Or perhaps the person who bought paid too much. Either way – consider it a dodged bullet… You don’t want to be in a house that stretches you too much. You don’t want to overpay.
Being resentful to people who see opportunity and take it isn’t going to change the system… just give you a headache or ulcer. Life’s too short to give yourself self induced stress.