It's not that easy to just "hand back" a leased car if you don't like it or it has problems. The finance usually comes from a finance company, not the dealership, so there's three parties involved and it gets very confused/stressful if it's faulty as you end up "piggy in the middle". There are also clauses in the lease about handing it back early (before the end of the term) meaning you often find yourself having to buy out the lease where the value of the "debt" is more than the trade value of the car. So basically, don't assume you can just hand it back and walk away, because in most cases, you can't and could be stuck with it for the full lease term.
As for older cars being expensive/unreliable, that's just a myth. The average car lasts 13 years and many last 20+ years. Driven carefully and serviced properly, a car shouldn't need much in the way of repairs and is highly unlikely to break down. Maybe when they get over 10 years old, there's higher risk of repair bills and breakdowns, but it still comes down to how it's driven and having it regularly/properly serviced to service schedule.
Of course if you buy second hand, you don't know how well/badly it's been driven before you, but you do have visibility as to the MOT history showing mileage and previous faults/problems highlighted at previous MOTs and you should go for full service history meaning the service handbook will be stamped by the garage showing dates and mileages etc, so plenty you can check out, and of course, you can pay for an AA/RAC check to have a mechanic check it over for any obvious problems (to a mechanic) such as condition of brakes, suspension, etc.
One of our current cars is now 18 years old, bought outright from new, never failed an MOT, never broken down, and never needed any major repairs beyond service schedule items such as battery, brake pads, spark plugs, tyres, new timing belt at 20k miles, bulbs etc - certainly no suspension parts, no exhaust, no gearbox and no clutch replacements needed. A previous car we got up to 190k miles was the same - just "consumables" needed replacing at services and never broke down.
Yes, "some" car models have inherent faults, but thanks to the internet, most are now widely known and a quick google of the specific make and model will usually throw up any known issues for cars to avoid.