Polygon & "optimistic roll-ups" are generally referred to as L2. In general this part of the etherum ecosystem is just starting up and the only one that has see

Polygon & "optimistic roll-ups" are generally referred to as L2. In general this part of the etherum ecosystem is just starting up and the only one that has seen much adoption so far is Polygon (which did 4M tx yesterday & still has low fees). Using an L2 system will mean that your user will need to be using that specific L2 system as well, but the UX doesn't seem so bad (at least for ETH -> polygon, and for the cryptocurrecny space so far). ETH 2.0 will reduce gas fees somewhat on the mainchain, but it's fairly obvious that there's huge demand, the sharding that ETH 2.0 will do is create 1 shard for execution & 63 for data only. Most L2 systems will mostly use the data shards, so we appear to be heading towards an L2 future. In short if I were building a company in the space I'd be looking at deploying both on the mainchain (L1) and on a L2 system, but prioritize the L2 system. Unfortunately we may end up in a world where there are dozens or more L2 systems and either the users or the companies have to pay the cost to hop between them.