For Bitcoin to pass whatever glass ceilings it has, it probably needs at least enough TPS to process all of the world's large, high value transactions such as houses, cars, yachts, etc.
At 7 TPS, you can do 604,800 transactions per day (probably closer to 500k in reality but whatever).
There are 14,000 houses and 43,000 cars sold per day in the US. 1 meg blocks are probably too small, or dangerously close to maxing out if handling all of the world's house and car transactions. We don't need to scale to gigantic blocks, but something like 8-10 meg blocks is probably what it needs to scale to for being a major player in the world, without a glass ceiling, where most things of several thousands of dollars in value are done on-chain. This is an achievable goal without things like the Lightning network existing.
You cant expect 8-10 meg blocks will work forever. First, if you agree once there is constantly higher demand than the blocksize allows to use, the Bitcoin will become highly unrelieable (long tx confirmation times + many transactions will never confirm because simply there is constantly higher demand than the blocksize allows to use). In such scenario it really doesnt make sence to use such unreliable Bitcoin and all will look elsewhere for a working altcoin.