Short answer - Intel 7 was "full stack" - all server, workstation, desktop, and mobile use cases, and no "new node" has provided the volume or range of chips to fully replace everything Intel 7 provides.
Details:
Intel 4 produces mobile chips only (Meteor Lake), is of (very?) limited volume, and has a performance regression in some areas vs Intel 7 products, thanks to going from monolithic to chiplet/tile design (+ latency), and a clock speed regression (H/HX). So Intel 4 can't even fully replace Intel 7 mobile.
Intel 3 is mainly server chips right now, also (relatively) limited volume (Intel tends to manufacture server chips on multiple nodes anyway over time). Intel 3 can't fully replace Intel 7 for server products.
... Neither Intel 4 or 3 serve the desktop market in any significant way.
TSMC N3B - I assume is higher volume than Intel 4/3 for Intel products, but there are no server products, mobile and desktop only; desktop is "full stack", though no workstation class parts (i.e. Xeon W). mobile is more or less fully covered. OEMs were not impressed with Arrow Lake at launch.
Bonus 1 - Intel is replacing a lot of Raptor Lake products that failed

- driving some more volume to Intel 7...
Bonus 2 - I've heard of rumors that Intel mandated OEMs buy a certain amount of Alder lake then Raptor lake (old Intel pressure style under Pat), so that may have obligated the OEMs to a certain amount of Intel 7 products even in 2025. Source is 'Moores Law is Dead', which Daniel Nenni has appeared on a few times.
Bonus 3 - Intel 7 has some 'niche' class products that no other node has, i.e. Alder Lake-N -- products based only on the e-cores from Alder Lake, such as Core i3-N305, Intel N97, etc.