I agree. It's always been advisable to use an Agent, even seasoned landlords can benefit from professional advice & experience occasionally.
But, let's face it, Labour Party plans for changes ( & this S21 change won't be the only one) is going to make life more difficult for anyone in the business.
As the negative impact of successive adverse changes hits home, I suspect more smaller landlords to throw in the towel.......it's already started.
I don't think there will be a total collapse in BTL although short term availability of property will get worse than it currently is. I think it will evolve and the business model will change over the next few years. I think there will be a move to larger landlords, with more standardisation and economy of scale........I'm thinking along the lines of what Travelodge & Premier Inn have done to the hotel industry.