A big complaint about routeros6 is the time it takes for a full BGP table to converge - especially on the top-of-range cloud core routers.

I don't deal much with IXPs, but I did hear somewhere that there were a shockingly high number of mikrotik peers at one exchange point (10%+)

As a Network Admin at an ISP in Brazil I can confirm their products are extremely popular due to the basically unbeatable price to performance and especially price to features. I can't think of anything close to their retail prices that can offer BGP, OSPF, MPLS, VRF, Wireguard, iptables, L3 hardware-acceleration, MLAG, ZeroTier, RPKI, VRRP, VXLAN, ECMP, Recursive Routing, LetsEncrypt, CA, REST API, etc. They have a 4x 10Gbps switch that has all of these features for $150.

You could potentially build a Linux PC to do some of the more basic stuff that most ISPs require at a similar price, such as PPPoE concentrators, but it's still a lot more hands-on work for no clear benefit.

I can't find right now what the market share of peering routers is in Rio's IX, but i feel like it's significantly higher than 10% (probably between 20 to 30%).