philately is a great hobby but I don't think that many people on this BIKE forum will be able to help you.
The trick is to not allow our previous experiences to cloud our judgement of the present. Learn from your experience of buying a pig in a poke last year, now you know to look for any airline cracks. If you are looking at a carbon fibre frame I would stick to new in most cases. If you are thinking of buying an aluminium bike just make sure you give it a thorough going over. I have bought heaps of old bikes in the past and have never come across any real issues. You may have had really bad luck on your first time out don't let that put you off. LBS can be a daunting place at times and can feel cliquey. That shouldn't stop you from voting with your feet and buying from an LBS that you get to like. The shortages of bikes because of the pandemic will not last very long and you will find that if you hold on a few months you could end up buying a cheap low use bike off someone that decided to give cycling a try over the coronavirus crisis and didn't like it.